BAC Forum
General Boards => Technical Support => Topic started by: Bill Drout on February 04, 2021, 12:27:03 PM
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My 98 Patriot cranks but will not start. My suspicion is that it's a failed CAT ECM, but I'm trying to follow the correct diagnostic procedure before condemning the ECM.
This post was very helpful:
http://beaveramb.org/forum/index.php/topic,6777.0.html
Here are some symptoms and/or data points:
1) When the ignition is switched on, the Allison shift pad lights up.
2) No check engine light. If I hold down the resume button for 20 seconds, I do not get the 55 flash code (or any other flash code).
3) If I turn the key to on, the speedometer test cycles but the tachometer does not. It's my recollection that they both used to test cycle.
4) I do not get a tach response when I crank the engine. I would expect it to jump to 200 or so. The needle appears to actually drop below zero on crank.
5) I used to get a light for the heated air inlet, and I would wait until that goes off before starting the engine. But that light no longer comes on.
6) Engine Warning light illuminates when the ignition is switched on, but I believe this is normal.
7) And the obvious: Engine cranks fine but does not start. It's not an intermittent start. It won't start at all.
Other data:
1) The two 10A fuses in the Allison VIM box are good and are getting power.
2) CB21 (Ignition Power Relay) and CB22 (Ignition Service Board Transmission) appear to be good. I understand from the post above that they could be intermittently failing, but my symptom is a "no-start" and not a "sometimes no-start".
3) The Bosch relay back at the battery bay is good. I'm thinking the relay is the "ECMR" (ECM Relay). There's a sticker in the battery bay which bears little resemblance to the actual wiring back there, but it has a picture of a relay pinout labeled "ECMR". I'm pretty sure that's what it is. I'm guessing the pick wire going to relay pin 85 is ultimately coming from CB21 in the front electrical bay. I'm also guessing that the Normally Open (NO - relay pin 87) is going to the J1 pin 70 of the Cat ECM. But I'd like to verify that.
Does anyone have the wiring diagrams for a 1998 Patriot?
I have been looking at the diagrams for the 1996 Patriot on a Magnum chassis in Coach Assist, but those schematics are for the CAT 3126, and the 98 Patriots have the CAT 3126B. That's relevant because CAT changed to the ADEM III ECM on the 3126B in 98. That ECM has two 70-pin connectors with different pinouts from the previous model. I can find some generic pinouts from CAT for "typical" connections, but I'd prefer to see the actual diagrams for this coach.
My next approach is to pull the J1 connector on the ECM and test for switched power on pin 70, constant power on pins 52 and 53, and a good ground on pins 65 and 67. If all of those check out, is that sufficient to make the call on a bad ECM, or do I need to check for something else first?
Any assistance or advise would be greatly appreciated.
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Bill
The relay you're talking about is the ECM relay and it provides power to the ECM upstream of that relay there should be a small ATO style in line fuse holder with a 20 amp fuse in it which provides the ECM power that fuse holder should be somewhere between the batteries usually directly connected to the batteries and the relay if that fuse is blown there's no ECM power.
The relay itself is controlled by the service panel switch a loss of power to the panel or bad switch may cause the ECM relay to not function also check the ground for the ECM relay.
I personally had a problem with the service bay switch on my coach it became intermittent and would not switch back and forth probably due to corrosion caused by debris thrown by the back rear wheels up into the service panelI have since installed a mud flap to stop the dirt and debris from being sprayed up there from rear wheels.
The dash ignition switches are also known to go bad.
You're going to need a good wiring diagram for the 3126b you need to be checking both power feed and grounds they'll be fed to the processor through a twisted pair.
If you are correct there is no power to the ECM at this point plugging a scan tool in will give you no communication the scan tool also picks up its power from the diagnostic plug which is fed by the ECM power along with the J1708 protocol.
AsI have stated in previous posts ECMs very seldom fail on their own, there are rare cases but usually they are murdered meaning and outside force like a voltage Spike reverse polarity shorted wiring etc kills the ECM .
It's been my experience many ecms have been replaced for no apparent reason the later cause usually found to be poor wiring or bad connection usually on the bodybuilders side cat as well as most OEM engine production people do a pretty good job on their own wiring harnesses but they cannot control what's the bodybuilder puts in, that would he where I would where I would concentrate my efforts.
Dave Atherton may be able to help you out with an accurate wiring diagram for your 3126B to help pin out the ECM wiring ,as for the coach builder side I would believe that the 1996 Patriot wiring diagram should be fairly close as Beaver didn't like to change things much from year to year
Hope this helps some feel free to ask any questions you like.
Good luck
Eric
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Bill,
Since your coach has the Magnum chassis, most of the early e.g. 1997-2004 coaches using the 3126B should have the same or very close wiring. The 2002 Patriot had a 3126B but the 03 had a Cummins. Both are covered in one set of dwgs in CA.
Steve
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Diesel Engine Trader has a forum post with similar CAT ECM problem (different CAT engine). He solved the no start/no check engine light by basically resetting the ECM. He pulled all power to ECM for a few minutes and reconnected (had to do it several times for some reason). I think you actually have to pull chassis battery cable since ECM is power is tapped off before any isolation switch.
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All,
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Steve
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Many thanks to the input I've received from everyone.
My coach has the Racor fuel/air separator for the fuel system. I ran the air purge and it looks good to me, so I don't think that it's an issue with air in the fuel line. I understand that this is not a definitive check of the fuel system, but it does appear normal to that point.
Given the way the problem developed and the new information received from the testing I've conducted, I'm really starting to think it's the ECU.
The IntelliDrive module gets no sensor data from the ECU, but it's getting data from the Allison transmission just fine. Values such as air inlet temperature, coolant temperature, and battery voltage show zero values on the IntelliDrive while transmission temperature shows to be normal.
As previously mentioned the speedometer test cycled when switched to the IGN key position, but the tachometer does not. The shift tower lights up and show "N".
I pulled the J1 connector from the ECU and tested for voltage and grounds. Pins 52 and 53 show constant 12V. Pins 65 and 67 show a good ground. Pin 70 shows a good switched (IGN) power.
With the J1 connector removed from the ECU, I'm getting exactly the same behavior (no data to Intellidrive, tach dead) as when the J1 connector is attached.
There's a shop in Fort Worth that will repair a CAT ECU for substantially less than what I would have to pay to get one from CAT. They say they can fix most ECU's, and there's no charge if they cannot. The service charge is $129 if they find nothing wrong with the ECU. I'm thinking that's the way to go as long as I can get the ECU out of the coach -- which is not a trivial task given all of the stuff surrounding it. I'll let you know how it goes.
Thanks again for your help!!
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Bill, I had the same problem with the switch in the service compartment. Shut me down completely.
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Hi William,
Did you also have power going to the ECM and no data being received from it at the front of the coach? That's what has got me thinking that it is the ECM and not some external electrical or fuel issue. The ECM definitely has good power and grounds on the pins that, according to my research, should have power and grounds.
On my coach I have an engine start and stop button in the service station, but I don't have a switch like a key switch. I also don't have a battery disconnect switch for the chassis batteries. I have always thought that to be strange. It may have been there originally, but it was gone by the time I bought the coach. And it was probably not in the service station since that area appears to be original.
The reason why I'm asking is that I've got the ECM out of the coach and ready to send in for diagnosis. If you had the exact behavior then maybe I have a flaw in my reasoning.
Hi Eric,
Do you have a recommendation on a scan tool to use for communicating with the ECM? I hear what you are saying about making a premature call on a bad ECM. I'm thinking that a bad switch in the service bay of the coach would keep power from getting to one of the pins (probably switched power on pin 70), and I'm seeing power everywhere I would expect power.
Also I have a theory on why the ECM may have failed. My batteries have been weak, and I've been putting off replacing them because I need to take the coach in for service that was unrelated to this issue. It's been my experience that shops are notorious for leaving stuff on and and flattening batteries. Then they recharge them and don't tell you, and you only find out about it 2 months down the road when the batteries fail on you. I was putting off replacing the batteries until I got the coach back from the shop because I didn't want to risk flattening a brand-new set of batteries. During my research on this issue I've discovered that low voltage, or voltage spikes (perhaps from using the boost switch) are pretty hard on these ECM's. It's just a theory, but that's my thinking on why the ECM died.
Hi Gene,
I also took in to consideration what you mentioned about disconnecting the chasses batteries. I have done that several times just in the course of diagnosing. I even disconnected all positive and negative wires from the chassis battery and touched them together in case I need to discharge a capacitor somewhere.
Thanks again for everyone's input!
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Bill, Does your coach have a "rear run and start switch"? From following this tread it sounds like a 22 year old switch in a hostile environment could be the culprit. The switch center pin or connection is the output, bottom pin is the ignition power from the front when the key is on, and the top pin is 12 volt chassis power from the rear. (I may have that info transposed) Please advise, Fred
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Hi Fred,
I do have a green start and a red stop button in the service center at the back of the coach. I'm guessing this affects power to to the ECU. Does anyone know how?
I see the wiring diagrams for the Patriot 2002-2003. The closest thing I see is drawing 38030067 with the title "C12 Engine Harness - No Serv Center". Mine is a 3126B with a service center from 4 years earlier, so it's not the best overlap. However it does show the CECM connector which would be to a dual 70-pin ADEM III ECM like mine. The "CECM (Engine Connector)" table on drawing page 2 of 2 does show the wiring harness with pins 52 and 53 getting constant 12V. It shows pins 65 and 67 connected to chassis ground, and it shows pin 70 to switched IGN power. All other pins are for communication in some form. All of this corresponds to the best information I have on my coach, and it matches the actual measurements of the J1 harness on the coach. Still crank but no start, a dead tach, no check engine light, and no ECM communication to the Intellidrive.
That's why I'm thinking it's a dead ECM.
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Bill, My unit was running fine when I killed it at the campground. Four days later, nothing. Crank and crank but no start. On my 98 tourmaline , there is a 3 way toggle switch in the service bay for front start, off, and rear start. My mechanic connected a lap top to a port in the service bay and found there was no power to the ECM. He then traced the problem to the switch in the service bay. He then bypassed the switch and bingo, back on the road. I hope this helps.
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Bill I am by far no expert, but if you have power to your ecm then I doubt that your rear start switch is the problem.
As far as the battery cut off switches, my coach does not have them either, and never has. I am in the process of adding them when I get a day off with good weather. It is one of those really not needed but I want it options
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Bill
As for scan tools the best you will get for your Cat engine is the Cat software as none of the other aftermarket units will give you as much access to the systems or function test ability as the Cat unit .
That said I've used J pro software to access mine and it did what I needed to do but it's also a very expensive commercial scan tool and if all your going to use it on is your Cat engine the Cat tool would be the tool of choice.
As Dave points out a full access commercial scan tool can be a dangerous thing in the wrong hands I've seen more than one ECM with bad or no programing left after a botched reprogram by someone who didn't know what they where doing .
The switch I spoke of earlier is the same toggle switch referenced in the last post it controls the ECM relay located in the top left side of your battery bay it basically switch's the ignition feed signal from the driver's station ( ignition switch) to the service bay switches. most busses are set up this way so you can kill the driver's station controls when you are working on the engine for safety reasons.
The relay switches circuit # 201 which is the ignition power to pin #70 on your CECM.assuming yours is as you say a CECM
That switch has a bad habit of having poor or no connection inside usually because of corrosion and age or inactivity.
If the coach was just in for service there is a good chance the tech may have used that switch at some point and now it's starting to give you problems.
How ever you say with the ECM out of the coach and the ignition on you have 12 volts + at pin #70 ignition power feed this is the wire which comes from the ECM relay known as circuit #201
You should also have 12 volts + on pin numbers 52 and 53 these are battery power feeds.
Don't forget to check the grounds to the ECM as well those should be pins number 67 and 65.
If you are certain that you have all of the above and still get no communication from the ECM then it would be time to sent the ECM out to be checked.
If the ECM is not powering up it will be doubtful that you will see any communication with a scan tool or anything else connected to the data buss like your silver leaf or Magnum inteldrive system.
I have seen processors killed by overzealous battery chargers but usually there done right there on the spot , most natural ECM failures are thermal cycle related the others are as I said in an earlier post they are murdered.
The engine builders like to mount the ECMs to the side of the engines to ensure they kept there wiring to a minimum and this gives them control over there side of the wiring but at the same time it exposes the ECM to the there so cycling of the hot engine.
The 1996 Patriot wiring diagrams show the ECM relay wiring on page 18 the pin out at the ECM may be different with the CECM configuration but the circuit should work the same way.
Hope this helps
Eric
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I decided to go ahead and ship the ECM off to 1EngineControl in Fort Worth. I requested a tech report on the ECM which should give us a good idea of what failed on the ECM. If I'm wrong (not a bad ECM) then the diagnostic fee is $150. That's still worth it to me at this point in time. I'll let you know what they determine.
This thread had a lot of discussion about the service bay configuration. In case anyone else finds this thread and is interested, attached is what the the 98 Patriot service bay looks like - including the "Engine start" and "Engine stop" buttons. During troubleshooting I tried to start from the back (with the IGN switch on) with no success.
To the extent it's helpful, I can give some ECM details for anyone else that may go down this path. The ECM is secured to the engine underneath the intake manifold by four 13mm bolts on stand-offs with shock mounts, and it was pretty hard to get to. I ended up removing air cleaner and the air cleaner mounting brackets to access it. Even so, getting to the bottom right bolt was quite a challenge. It's up against the engine mount secured against the C-beam. I finally got a box wrench on it coming in from a very narrow passage from the transmission (coach front) side. The 70-pin connectors are 4mm (~5/32") allen head bolts. There's a braided ground wire that attaches from the starter to the top left bolt and routes from the starter between the J1 and J2 connectors to the top left bolt. A smaller braided wire also attaches to that bolt and is secured to the case of the ECM.
The one up-side to each challenge I encounter is that I know the coach better than I did before I had the problem. That could end up really helping me one day if I need to make a trail fix somewhere.
Thanks again for everyone's input!
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Bill
The place you are sending the ECM out to will need some info from you is
1 ) the ECM serial number
2) rear end ratio
3) tire size
4) transmission make model
5) idle speed
6) engine max speed
7) cooling fan configuration
8) jake brake con if any
9)max road speed set if any
@0) max cruise speed if set
If the the rebuilder is cat licenced they should be able to get programming from cat using your ECM serial number.
Usually it easier with a working ECM to retrieve the existing programing
At any rate I'm sure a reputable rebuilder will be able to get you set up with exceptable programing .
PS.. nice spot to work in down there isn't it even worse with grease and road grime.
Make sure to keep those ECM connectors clean and inspect all the pins for bent or corrosion.
Don't loose the bolts or stand offs.
Keep us informed as to your progress
Good luck
Eric
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Hi Eric,
I talked to Anna at 1 Engine Control a couple of times on the phone to make sure they had the information they needed. She was very helpful and took time to answer all of my questions. Apparently all they need is the engine serial number, but they do have my email and phone number in case they need to contact me. I also explained that I wasn't trying to do anything custom. I want the ECM to work just like it did before.
Apparently most ECM repairs can be performed without programming/reprogramming. It sounds like there are some discrete components within the ECM that can be replaced without impacting other parts of the ECM. I guess the memory portion of the ECM is not usually the part that fails.
One of the benefits of going with 1 Engine Control is that they will preserve a copy of my ECM config file once they have it fixed. They will also send me a copy for me to keep. I hope the ECM never dies again, but if it does at least I'll have some more tools and information at my disposal. They can also overnight me a replacement ECM if I'm ever stranded.
Duly noted on keeping up with those stands and bushings. I kept track of them along with which corner they came off of so I can put them back in the same spot they came from.
Thanks again!
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Bill,
Your service bay is almost exactly like mine, but I have two more air bleeds. I am not sure why, but I included a picture in case it is helpful to anyone in the future. Good luck with your ECM and let us know how it all works out.
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Bill
It's always a good idea to keep a clone file of the ECM programing as sometimes there are suttle differences even between like models horse power torque etc. Not to mention things like fan control or pto programming that's the reason a clone file becomes important as it allows you to return to the original programming if something catastrophic happens to the ECM.
And as you said it's nice to have a copy of that at the ECM supplier in case you have problems on the road somewhere.
Hope all goes well.
Keep us posted
Eric
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Hi Carl,
That's really interesting. Our service bays are very similar, but you have an on/off switch and I do not. And you have those extra air valves. Does your coach have an air dump button on the dash?
One other question since it's in the picture: The green power light on my Racor Fuel/Water separator is always on. The only way I know of to shut it off is to disconnect the battery. That doesn't seem right to me. Is that the way yours behaves too?
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I do have a air dump on the dash, and the light does not stay on,but then again I have never noticed it being on. I guess I'll have to check it out the nest time I crank it.
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The ECM got to 1 Engine Control, and they are saying that the unit does need to be reprogrammed. I do not have a copy of the parameter file, so (as Eric mentioned) they are now asking me a bunch of questions, some of which I do not know the answer to. Attached is the form. The rebuilder said they could take the engine serial number and set to defaults.
Does anyone know if Beaver made any customizations to the parameters for the coach?
Does anyone know of another 98 Patriot owner that might have a copy of their parameter file? I'm wondering if it makes more sense to start with that than to take engine defaults.
Thanks!
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I am sure Eric, or Fred can answer you more accurately, but I don't think Beaver, or Safari varied from the Caterpillar settings. I do know that you could get a 300 hp or a 330 hp option. Mine has the 330 hp engine.
I could not open the attachment, but that could just be my computer, so I don't know if there is any more questions I could answer.
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I know that our own Dave Atherton has 'pulled' engine parameters from his CAT computer using the engine serial #. Perhaps a call to Dave is indicated. Or a CAT dealer could do the same, but its gonna cost you some scratch!
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I called the rebuilder. Apparently they had overlooked my serial number that I had sent with the ECM. I gave it to them again along with the coach VIN and mentioned that it came out of an RV and not a truck. Apparently that was all they needed.
Attached is the technician check list that has some comments about what was found. It doesn't say much besides "Faulty Battery" and "Bad data line". I guess the ECM has a battery?
The document doesn't give much insight into why the unit malfunctioned, and that's unfortunate. I'm trying to determine if the failure was self-inflicted, and if so, how to avoid a repeat.
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I wonder if your issue is related to this thread. http://beaveramb.org/forum/index.php?topic=563.0
Now thinking I should check my c13 ECM to make sure it has necessary updates.
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Bill
As you said the report doesn't give you much to go by.
It appears the ECM suffered an internal power supply failure.
With out a power supply the processor won't come to life and therefore there will be not activity available for serial stream data and of course not data buss activity so no data can be extracted via the diagnostic link as it is connected to the data buss.
This explains why the report states no data and hence fault codes and of course no access to the programming.
As for the cause of the failure this is the kind of think you would expect from a reverse polarity , voltage spike or run away voltage it's the type of failure that can be caused over time as the result of a reoccurring stress such as a voltage spike caused by a defective or missing clamping diode or resistor on a relay circuit allowing the collapsing magnetic field of the relay coil to create a voltage spike.
Before reinstalling your new ECM check your inverter charge voltages as well as any solar charge controler voltages.
As you have already tested the powers and grounds to the ECM so we know there shouldn't be any reverse polarity issues.
Once you get it up and running make sure to check the alternator change voltage as well.
Also check and clean the ECM ground strap as well as the ground connections at the back of the starter and any engine to frame ground cables.
ECMs don't like dirty or noisey power that's why most ECM power is supplied straight from the battery as the battery works as a capacitor /shock absorber to reduce electrical noise.
With a working ECM you should be good to go.
Hope this helps
Eric
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Gentlemen, may I suggest your problem No start could be number one let’s go to pin 70
Red wire that is on/off off key switch. This red wire provides 12 volt from key on/off direct to the ecm
Lower left corner on J-1 cable data to front of motorhome. Before going deeper at the ECM power
Let’s disconnect the IAP sensor from engine wiring along intake manifold wire loom. What you are looking for is a triangle connector connected to a 15 inch pig tail that connects the IAP sensor to
engine. With the IAP sensor disconnect try to start engine, if engine starts and runs the IAP sensor
Is bad and needs replacement. Dave Atherton Retired Cat Mechanic
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IAP sensor - Intake Air Pressure sensor?
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Gentlemen the sensor IAP sensor ( injection actuation pressure sensor ) has a 15 pigtail to
Triangle connector. Dave Atherton Retired Cat Mechanic
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Bill
from a little bit of research I've done I've discovered that the ecms or cat ECMs do have an internal battery
the internal battery were first put into use in 1993 to maintain power to new type of memory' chip eprom or (erasable programmable read-only memory ) this memory contains programming and calibrations .
when the battery goes dead everything can continue to work fine until the vehicle battery goes dead or is disconnected once that happens there's nothing to maintain the eprom's memory and you lose your programming it would appear this is what's happening in your case.
Hope this helps
Eric
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Thanks for everyone's input so far -- I know it's been a while. As you probably heard (or experienced) we had a really cold snap here in Texas, and I've been preoccupied cleaning up from that for a while.
I did get the ECM back, and finally got it installed. The coach cranks and appears to run just fine.
BUT...
1) The tachometer pegs high when the engine starts (points straight down). The tachometer also appears to have some "jitter" around 0 during key-on, engine off (before starting). The Intellidrive displays a tachometer reading that appears to be correct. It responds to the a change in engine speed like I would expect as well.
2) Cruise control is INOP. It will not set in neutral, and it will not set when up to speed and going down the road.
3) The shift pad is not as responsive as normal. Sometime I have to press it 2 or 3 times in order for it to detect the input. I have no idea if it's related to the tach/cruise issue, but it's definitely a change in behavior.
4) The J-II leveling system warning bell tone sometimes will change. At other times it will be normal. When sounding irregular, the tone returns to normal if I press the boost/bond switch to join the house batteries to the chassis batteries.
5) The Intellidrive restarted when I was using the J-II controls to level the coach, so I'm guessing that was from low voltage.
So, in conclusion, I'm pretty sure that I still have gremlins in the electrical system, but I do not know if that is causing the tachometer/cruise control issue or if it is an ECM issue. The tach and cruise control worked fine the last time I drove the RV before the ECM failure, so I'm suspicious that it's ECM related. Nonetheless it's possible that the electrical issue is causing the problem, so I'm troubleshooting that to start off with. It's also possible that the gremlins caused the ECM failure to begin with.
I'm suspicious of a weak ground or a chassis 12V connection somewhere. The initial check looks good in battery compartment, and that was my prime suspect area. I have new chassis batteries (about 1 month old now), so I would not expect that to be the problem. I also cleaned terminal connections when I replace the batteries.
Another prime suspect would be the continuous duty solenoid in the electrical bay, but I replaced that recently.
Everyone has been very helpful so far. Let me know if anyone has jewels of wisdom.
Thanks again (and in advance) for your help!
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My first guess would be a ground issue also. I would jumper a ground wire from the tach ground back to a good grounding point maybe in the electrical bay and see if that improved anything. If so great, if not I would start testing the signal wire. There are a lot of wires and connection points in our RV's.
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The following file is a cat document that goes through the reasons for a no start, I have attempted to attach this before with no luck, I just sent it through email today. Please let me know if you can get to this attachment or not?
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Bill
Looking at the wiring diagram for the 1996 Patriot it shows the tach driven by the alternator tach drive the 98 may be the same
If so I'd be looking for a ground issue to theta h and maybe to whole front electrical bay area .
With that said if you've had the batteries disconnect lately I'd look very closely at the cable routing make sure you have all the grounds in the right places ( you wouldn't be the first to have a cable drop down behind the batteries and not hooked back up.
The cruise switches are tied straight into the ECM but there is a brake interrupt relay that interrupts the cruise when brakes lights or exhaust brake is activated ( the cruise and or fast idle won't work with the exhaust brake switch turned on) .
With that said it would be possible a bad ground could effect the cruise via back feed through the cruise interrupt relay.
Hope this helps
Eric
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I think I found my gremlin in the battery ground. That has now been resolved, but I still do not have a responsive tach. The cruise still does not set, and the engine brake switch does not work either.
I peeked behind the front dash, and it appears that the tachometer is circuit 356 (see attached). This corresponds to the numbering for the "2002-2003 Patriot Wiring Diagrams" schematic "C12 Engine Harness, No Serv Center" page 2. For that coach the 356 Circuit maps to "CECM (engine connector)" pin 38 (ECM Tach Out +). I'm thinking it's reasonable to assume that it's the same on my coach as well.
Also according to that same schematic, all of the items that are not working have direct connections to pins on the ECM. I'm getting this sinking feeling that the ECM was not fully repaired. I have reached out to 1EngineControl and hope to hear from them tomorrow.
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Could it be that the ECM needs to be programed for those functions to work?
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Looking at the wiring diagram for the CECM that you are correct all those functions come straight from the ECM to the tach etc .
With that in mind there are the connection pins at the ECM plugs and connector # 51 near the e! electrical bay failing that it may be a programming failure in the ECM.
Let us know how you make out with your rebuilder
Eric
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Hi Bill L,
I'm _really_ hoping that's the case. I'm still recovering from the reinstall, so the thought of pulling it again will require some mental preparation :-) I would gladly drive the RV somewhere to have it reprogrammed over pulling the ECM, even if I have to pay for it separately.
Pulling the ECM off the side of that engine and reinstalling it was a bear of a job. Most of the work is done from underneath, and I'm working on it outside in an area that's just dirt and sand. You have to pull the air filter, the air filter mounting brackets, and the crankcase breather hose even to see the ECM. Even then the view of the ECM is limited, and your vision is almost always blocked because you have to put your hand though the same small field of view you're looking through to work on the ECM. Then to remove the 4 bolts that hold it on you have to be somewhat of a contortionist to get around the chassis C-beam that goes in front of it. I can't even see the bottom right bolt at all, so I have to wrap my arm over and around the C-beam and then get the wrench on the bolt (don't round it off) and loosen or tighten as appropriate totally by feel. The stand-offs are comprised of several different components, and many pieces have to be removed/reassembled by feel. Don't have any part of them fall down into a crevice and get stuck, because you can't see down there. Several parts are not metallic, so using a magnet to retrieve them will not work. Finding them will only be via the same Braille method used to remove/reinstall the bolts. I had to do that several times, and a few of those times I thought I would not be able to find/retrieve the part.
I'm not whining (okay maybe a little) -- just sharing. I'm sure we could all tell a similar war stories. This will be one of mine. I guess that's just part of owning an older RV.
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Bill,
To the best of my knowledge ECU programing should be via the diagnostic connector, either under the dash or in the rear run box area. There should be no need to pull the ECU. Dave Atherton should be able to confirm.
Steve
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Bill, after checking wiring would suggest going to back of your tachometer on top at 12 o’clock there
Is a Yellow wire and wire number 450 connected to pin 17 on ECM side J-1. Next at 6 o’clock there
Is a brown wire number 451 connected to pin 11 on ECM side J-1.
Note if there is only one wire on tachometer which the plus wire is Yellow and wire number is 450,
can be connected to either pin 17 or pin 11. Note one wire than should be left disconnected. The
Ground wire for tachometer should be attached to starting motor housing ground. After getting the
Tachometer working than can help with the cruise. Dave Atherton Retired Cat Mechanic
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Hi Steve,
Thanks for the heads-up. I do see a "Diagnostic Data Link" connector in the service center, so I'm thinking that's the place to go. If it's just a programming issue then I agree that someone can probably do it with the ECM still in the coach. I'm just hoping that it's not an overlooked component (hardware) failure inside of the ECM.
Hi Dave,
Thanks for looking up that information for me. I took a peek behind the dash at the tachometer, and I do see the signal wire going to the tach. That wire is labeled "356 Tachometer" on my coach, but I think we're talking about the same connection going back to the ECM. I'll respond to this thread once the rebuilder gets back to me -- hopefully today.
Thanks again!
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Bill, I do not know where you are located but if you take motorhome to a cat dealer your problem
can be corrected with Caterpillar service tool call ET. The same time so an your other functions can
be corrected. I take it you bought a ECM that programmed off the engine. The cruise control has a
Soft or hard setting on down shifting that can be set with Cat ET service tool. Last my suggestion
would be after your ECM is operating correct for your motorhome than have a copy made up of all
information on your ECM to carry with your motorhome. If this cannot be preformed having copy
made for a backup , I can print out your information at Quartzsite in January at the beaver rally
In the desert. Last when I connect my ET for a Diagnostic ECM readout/ printout this is information
many beaver members all ready have for there motorhomes. Dave Atherton Retired Cat Mechanic
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Hi Dave,
Yes it may be time for a trip into Mustang Cat in Bryan, TX. The response I got from the rebuilder was that they set the ECM parameters to something that they thought was similar, but apparently it was not identical.
One of the things they are asking me for now is the PPM (Pulse Per Mile). Apparently that's a parameter they need to configure the ECM for proper function. Would CAT know this if I took it to them, or would they be asking me for it too? I'm guessing that's specific to a Beaver motor coach. The rebuilder said it should be in my owner's manual, but I'm pretty sure my Beaver owner's manual would not have that. If I had to guess it would have something to do with tire size, but I don't know that for sure.
Does anyone have the PPM value for a 1998 Patriot? If not, would this be something that Beaver Coach Sales might know?
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Bill, the caterpillar service shop is well aware of setting a ECM using Cat ET on your motorhome.
Been down this trail many times and one thing cat service, may remove your valve cover so they
can get the numbers off electronic injector personally code. Guess I’m not to woozy ordering a pre
program ECM just for the reason you are having. One question I do have, did your ECM just shut
down your engine than a no start or how did a determination bring you to the ECM. Reasons for
this question it is very rare for failure in this area. Dave Atherton Retired Cat Mechanic
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Hi Dave,
Everything related to the ECM (speedo, tach, cruise, exhaust brake, etc) worked just fine prior to shutting down the engine the last time I had run it. I came back a month later to exercise the coach only to find that she would crank but not start. The tach was not responding during the crank, and I had no check engine light test come on when switching the to key ON. I also could not get the ECM to give me any flash codes - not even the "all is well" 55 flash code. I had no engine data (like intake manifold temperature) on the Intellidrive with the key switched on. As far as I could tell I was not getting any signals from the ECM, and the coach would not start. After a lot of troubleshooting and as a last resort, I got down to removing the ECM J1 connector. I confirmed pins 52, 53 had good constant power, pins 65, 67 had good ground, and pin 70 had good switched power.
At that point in time I made the call that it was the ECM. I pulled it and sent it off for repair. The tech report diagnosis was "faulty battery" and that they could not retrieve the original settings off the ECM. So they said they programed it with the profile for an RV. They sent it back, I installed it, and here we are. The coach runs but the tach, cruise, and exhaust brake are inoperative.