Beaver Patriot Thunder Won't Start

[Edward Buker]

Tom,

The transmission has to confirm it is in neutral before it will allow the engine to be turned over, so that is the main problem at hand to be fixed first.

As far as the starter, there is not much trouble shooting to be done until the keypad works and you then may not need to troubleshoot the starter if you can sort out why the display is not active.

Just a little info on the wiring on the starter, if you find you do need to go there. The large wire that is tied to the solenoid, that is powered on all the time, is the main 12V feed. One of the smaller yellow wires that is tied to the small solenoid terminals is tied to the key start contact that enables the starter to crank over. Between the key start switch and the starter solenoid, the transmission pad logic makes or breaks that electrical path based on whether neutral is confirmed. When the small yellow wire is energized from the key start contact to the solenoid, it powers a wire coil electro magnet that causes the starter gear to engage to the flywheel, and at that point it makes a large 12V contactor inside the starter solenoid connect the large 12v powered wire on the solenoid to the starter motor windings and armature and then cranking begins. The other large wires on the back of the starter are ground that have no voltage on them.

So the neutral switch has to be made first to enable the path. There is one more obscure possibility. Cat has an anti theft circuit, that if somehow it inadvertently was set to protect the coach, that could also disable starting.

Wish I knew more about the transmission logic and wiring but I never had to go there so hopefully there are better sources for help out there that can get you through that trouble shooting. Hope this helps.

Later Ed

[Edward Buker]

Tom,

One more thought.....Cat was able to get the rear run switch option to power up the coach. Have you checked to see if the rear start option still works and if it does, that must then power up the Allison pad. If that is true you could see what wire is toggling 12V on and off to that Allison control pad with the rear start that is not active from the front start and trace how that wire gets powered up from the wiring in the front of the coach. It may be that the rear start does not work now either, but thought this was worth a check.

Later Ed

[Tom Blad]

Ed,

The Cat tech initially could not get the engine to crank at all ( I also believe the shift pad was not lighting either) and he eventually connected a Cat harness to the engine. He said it started right up. I don't know if the trans pad lights up when it is started under these conditions or not. I am 99% sure that the pad was lit up when I started home with it as I remember checking to see if the red mode light was on as I was driving. At the time, of course I didn't know anything about the trans pad needing to be lit to function.  He then thought he had found the problem to be in the rear start switch and could reproduce the problem by manipulating the rear start switch. He replaced that switch and felt the problem was solved. I suspect he started the engine from both the rear start and front start position but don''t know for sure. I have tried to start from both front and rear and it reacts the same way (no crank and trans pad does not light.  I plan on going back to Cat today or tomorrow to clarify and also to see if they can offer any kind of off site assistance. The tech said that he started the engine several times over a couple of days and it started as it should. Then when I picked up the coach it also started as it should and also ran fine and started O.K. while fueling on the way home. The problem then began again after I got home and has been dead in the water since. I'm going to spend some time on the rear start area today and am contemplating replacing that rear switch along with the rear compartment light switch which is located right below the rear start switch. Don't know if they are wired together somehow or not.  Need to see if there is any power at all going to that rear start area.

Thanks,


Tom 

[Tom Blad]

I spoke with the Cat mechanic and he advised that once he changed the rear start switch the coach started right up. He started it from both the front and rear with no problems. He showed me the Cat harness he used to by pass the coach wiring and explained the pin# references he had on the invoice. Of main concern to him was pins 52, 53, and 70 (which in think is main power). Also the J19 which I believe is the communication link. I have also inspected both rear switches. The start switch looked good but the compartment lite switch had a broken terminal. I have ordered a new switch and will install in a few days. Don't know if that switch is in the start circuitry or not, but will replace it anyway. Does anybody know what this switch is supposed to do?

I have also located the ECM in the transmission console and will open it in a day or two to check for fusses. Very hard to get to it and to release the plugs. Also the two fusses in the VIM are good and I will change the 6 relays around that are in there to other positions to see if any of them are bad. Also the board beneath the shift pad has no fusses, but shows no outward signs of problem.

Does anyone know the route that the battery power travels to get to the VIM,ECU and transmission pad. Also how to determine which wires/pins to check for power. Does power go to ignition switch then to the VIM, then to the ECU, and transmission pad or does power go to the pad in a different order. I read on another forum where someone had a similar problem and eventually solved it by running a direct #10 gauge wire directly to the ECM or VIM and got power and solved the problem. Any ideas. Got to get that pad to light up.


Tom
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[Steve Huber Co-Admin]

Tom,
If you haven’t yet, you may want to refer to the Marquis wiring diagrams at http://beaveramb.org/coach-assist-members-only-2/  located in the Private BAC Members Only board. The Coach Assist post has the hyperlink to access them. Although they are labeled for a 2003 Marquis, the wiring for all Magnum chassis units is very similar and used pretty much the same circuit numbers, etc.

Power is applied in parallel to the functions you are concerned about. The source is the ignition buss in the electrical bay under the driver.
•   CB21= Engine ECU. It supplies power via wire 201 thru C4-1, C51-1 and C57-1 to the ECM relay.
•   CB24=Xmission ECU. It goes to C5-11 via wire 202 to C42-1.
•   CB27= Dash Inst Shifter Console. It supplies Instrument power via wire 211 to C4-19, Ignition Security System pwr via wire 614 to C4-24, and Ignition Pwr via wire 250 to C5-16.
The Circuit Breakers are thermal and trip when they get too hot and reset when they cool down. You can find the above in parts 2 & 3 of the Marquis diagrams

Also, there is a 20A fuse for the transmission VIM in the Fuse Module Tray (see diagram in Marquis Wiring section).

I suspect the pin #s the mechanic was referring to are on the engine ECM itself which does not appear to be covered in the diagrams above. I would verify the low amperage fuses in the Allison Control module before looking elsewhere as something happened between the shop and your trying to restart it. If you find a blown fuse, I’d check the area(s) the mechanic worked on for a bare wire that could momentarily short to ground.
Good Luck,
Steve

[Tom Blad]

Steve,

Thanks for the information. I did go to the coach assist section and downloaded all of the 2003 Marquis wiring information plus a couple of others. Have spent much of the day going over the material. Slow reading because I am not well versed in these matters. Very helpful. There are differences in Patriot Thunder and Marquis diagrams but since the wires are labeled I was able to identify most of the ones that might be relevant. I located what I believe to be the " fuse module tray" on sidewall of the battery compartment. There are 5 items located in there as follows:" ECM relay"The which appears to just be a 15 amp blade fuse. The second one is labeled as "service center" and is a 20 amp blade fuse. The third one is labeled "XSMN  VIM" and is a 20 amp blade fuse, the fourth is labeled as event recorder and is a 20 amp blade fuse. The fifth appears to be a larger relay (Seimans) labeled ECMR. The fuses all looked good and tested good for continuity. I am not sure how to test the relay or if it is necessary.

I plan to remove the fuse tray from the wall of the battery compartment tomorrow and see what color wires lead out of it and if they are labeled and where they might terminate up front. Hopefully then I can test wires for continuity and power. I should have the two new switches for the rear start box tomorrow and get them installed. I still need to open the ECU silver metal box up front and check for fuses,etc. Once all of the above is completed I'll give it try again. Probably looking at couple of days to get this done.

Thanks,

Tom

[Steve Huber Co-Admin]

Tom,
No need to pull the fuse tray. Look on the page following the fuse tray diagram. All are 14awg white wires. I'll still suspect your problem is a blown low amperage fuse in the allison box.
Good Luck,
Steve

[Steve Huber Co-Admin]

Tom,
This thread might be helpful.  http://beaveramb.org/forum/index.php/topic,4631.msg35142.html#msg35142
Steve

[Tom Blad]

I am still working on my no start problem.  One of the previous posters on another thread solved a similar problem with
a new PCB 1 board (starter control board)?  I have not been able to find one.  Does anyone know the location of that board or does my 2000 Patriot even have one?

I have found the black plastic Allison box in the electrical bay.  I believe it is called the VIM (vehicle interface module).  I have also seen it referred to as the TCM, etc/  It has two 10 amp fuses inside which tested good.  I also located the Allison ECU (also sometimes referred to as the main Allison computer).  It is a silver clam shell metal 6" x 6" box which had two  PCB boards inside.  There are no fuses inside.  There is a black plastic box directly beneath the shift selector pad containing a PCB and no fuses inside.  I have found only 6 fuses so far.  Two in the black VIM box and 4 in the battery box area fuse module tray.  Seems like there should be more than 6 fuses.  Am I overlooking some areas that might be relevant?

I have put in a new ignition switch up front and a new Comp light next to the new rear start switch.  I doubt that the light switch is relevant but one of the terminals was broken so I replaced it.  The ignition terminals and wires are labeled as follows:  Ignition terminal connected to wire labeled ignition power, Ground terminal to wire labeled ground
Battery terminal connected to a wire labeled battery power to ignition, Accessory terminal connected to a wire labeled accessory, and SOL terminal connected to wire labeled start.I do not know where these wires go to.  This is probably a real elementary statement but it seems logical that the whole starting process begins with the turning of the key, but I am not clear on routing of the power from there on.  Which part of the Allison communicates with the other parts and in which order.  Can anyone advise the routing of the power when the key is turned to start?

I am looking at replacing the solenoid in behind the battery compartment.  Not sure if this solenoid is part of the starting circuity or not but when I attempt to start I can feel and hear the front electrical bay solenoid activate as well as another solenoid in the ceiling of the battery compartment.  The third solenoid does not appear to be activated by anything.  Unfortunately it looks like all the batteries must be removed in order to access that solenoid.

I am also replacing the two chassis batteries as they don't seem to hold a charge as well as they should overnight.  I also have not been able to test power to the CAT installed rear start switch but will do that after I  replace the aforementioned solenoid in a couple of days and get the batteries back in.  I am also considering having the Allison shift pad, VIM, and ECU tested.  Does anyone know if Allison dealers do this type of testing?  I have a possible truck repair facility that will make onsite visit($$$$) and indicates that they have the necessary diagnostic tools and proprietary software for CAT and Allison and thinks they can probably solve the problem.  I would like to take the three Allison transmission items and have them tested before I  sign on for the onsite visit.  Any ideas or suggestions would be welcome.

Thanks to all who have responded.

Tom
       

[David T. Richelderfer]

I had a similar experience several years ago.  The link below will take you to the entry where I finally got my coach to start.

http://beaveramb.org/forum/index.php/topic,2701.msg20280.html#msg20280

The pertinent paragraphs:

"After chatting with Ken at BCS for five minutes, we learned there are two fuses just under a small removable four inch square plate on the generator.  One of those fuses, a mini auto-style 15a (blue) fuse was blown.  Now the generator starts.

"Ken said the problem with the C-12 not starting is the transmission MUST report to the engine that it's in neutral.  Remember, the transmission shift keypad would not light up.  Under the keypad there is a black box, accessed by removing the vertical door that holds the map pocket. In that black box you will find fuses.  One was blown.  Now the keypad lights up and GUESS WHAT, the C-12 starts right up."

[Steve Huber Co-Admin]

Tom,
If all fuses are OK, check for 12v coming into a-fore mentioned  transmission control boxes.  I'd expect it to be on the 10 amp fuses. If 12v is present, sounds like it is one of the boxes. As I posted earlier, I think wire # 202 is 12v to transmission ECU. If not and no 12v, ID wire # so you know what you are looking for in electrical bay, etc.
Steve

[Tom Blad]

Well, a lot has been going on with the no start problem. Some good, some not good, and most not explainable.
We have replaced the following items: 1. Front electrical bay (start ) solenoid. 2. Ignition switch. 3. Rear start switch. 4. Comp. light switch in rear start area. 5. Solenoid located behind the battery compartment (the most inconvenient place you could ever put  an item like this!) 6. New chassis batteries.
     Also we have cleaned most every connection we came across although most looked to be O.K.  except the rear comp light switch. Located all three Allison components (i.e Transmission shift selector pad, Transmission VIM, and main Transmission ECU). There are only two fuses total in the three components and they were 10 amps in the VIM box and both tested good.  I believe these three components are functioning O.K. as I will explain later as we were eventually able to get the engine started.  Also, there are four fuses in the fuse module tray which all tested good.
     While doing the above listed things we began to identify and trace wires as Steve suggested previously. One of the things we discovered is that the wiring diagram that is attached to the inside of the electrical bay door is not  accurate. For example, On the diagram CB22 says service board, XSMN, ECU, and VMS2. The wires connected to CB22 are actually labeled as #265 Ign Power VIM relay, #202 Ign ECU and #233 Ignition Power. Until we discovered this it made any tracing of the wires a futile effort. We finally identified the wire numbers and names on all the wires coming off he copper buses and will be tracing those as well as checking for continuity and power.

     Another major problem has been getting the proper schematics. I have down loaded over 100 pages from the BAC fourm and other sources and have had no luck in finding schematics for a 2000 Patriot Thunder with the rear start feature. I realize that many of the schematics I have examined apply to more than one model of coach. For example many of the schematics are for the Marquis, some are labeled Thunder, Montery, etc. There is a lot of over lapping of applicability between the various models but the one thing that is missing from all of them is ANYTHING dealing with the rear start circuitry. If anyone has ANY information or thoughts on this please advise. The whole wiring of the rear start circuitry is confusing. For example, the rear start switch, the comp light switch, the rear oil pressure gauge which is not working,  and the rear  water temperature gauge which is also not working are all connected or wired together in some way.  We have identified all of these wires but have not figured out how it all connects.

     Now, I mentioned at the beginning that there was some good news. We finally did get it started, however, it is an on again, off again situation.  Here is the time line and other details:

     1. After replacing and cleaning the previously mentioned things  for over 30 days and having no results, on Thursday 7/20 we started an attempt to identify and trace some wires. A the end of the day I turned the key as I usually do just to give it a try and low and behold the shift panel lit up and the engine started right up. I let it run for 10 minutes and I was able to drive a short distance and reposition the coach. Shut it off and restarted again as normal.  All was well and I shut it off for the night.

     2. 7/21 went out in the morning and turned the key and it started normally. Let it run for about 10 minutes and shut off. Did some more voltage checks, etc. and 3 hours later turned the key and the shift pad did not light and there was no cranking. Later in the afternoon we were again checking continuity/voltage from electrical bay to rear start switch and when I turned the key to accessory the shift panel lit up but the engine would not crank. I left the ignition switch on accessory and went to the rear start area and moved the switch to rear start and pushed the start button with no results. About 10 seconds later out of frustration I pushed the rear start button and the engine stated right up.

     3. 7/22 Attempted to start from both front and back several times with no result.  Transmission did not light up and engine did not crank.

     4. 7/23 Attempted to start with negative results. I continued  to test for voltage at rear start and wife turned ignition to accessory and the transmission pad lit up. I went up front and turned ignition to start and engine started normally. I shut engine off for a few minutes and then restarted normally. I did notice that the transmission light did blink momentarily and the "cat eyes displayed on the shift pad for 1 or 2 seconds and then went back to the normal display.  The engine continued to run normally. I shut it off for a few minutes and then attempted to start with negative results. Shift pad did not light up and no crank.

     5. 7/25 Went out this morning and attempted to start with negative results. No light in shift pad and no crank.

What all of this means I do not know. I do know that if the trans shift pad does not light up the engine will not start. Also that on one occasion the pad was lit up and it would not start from the front but on that occasion it did start from the back. I am leaning towards the problem being a bad/weak ground or frayed wire somewhere.  Today we are tracing wires and checking continuity. Also I am replacing the relay in the fuse module tray although it may be O.K.  Also I'm not sure about the factory label affixed to the battery bay door which lists the components of the fuse module tray  as ECM Relay which is a 15 amp fuse, XSMN VIM 20 amp fuse, Service center 20 amp fuse, Event recorder 20 amp fuse, and an actual siemens relay labeled as ECMR.  I assume the one labeled as "ECM Relay" is the 15 amp fuse and  is not itself a relay but puts power to the ECM relay.  After seeing the labeling on the electrical bay door I'm not sure what to make of this. One other thing, I would like to check the wiring to the back of the fuse module tray to check for corrosion but can't figure out how to access it. No screws are visible to take it apart.

This is a lot of information to digest but it is what it is. Not a simple problem to diagnose but am still hoping for a simple solution.

Any thoughts or ideas are welcome.


Tom




     

[Steve Huber Co-Admin]

Tom,
Symptoms sound like a connection or relay/CB that is intermittently failing. Since you know that the Allsion pad needs power for engine to start, consider focusing on it. If wire 265 is the Transmission VIM ign power relay, can you verify it has power in  a non-start situation? If it does, then verify that power is coming into the VIM box.
Steve

[Tom Blad]

Steve,

One of the things I should have mentioned earlier is that during a couple of the successful starts mentioned above I did hear one or more of the relays in the electrical bay clicking quite a bit. I had not heard this before. Couldn't tell which one in particular was making the noise and it may have been more than one. This chattering continued for several seconds after the engine started and then everything quieted down and the engine continued to run. This happened 2-3 times. Also during the time when we were replacing some parts earlier I did notice that one of the relays in the electrical bay had a discolored connector as though the plastic connector cover had gotten quite hot at some time. The connection itself looked O.K. but the relay was replaced anyway. This relay has 4 terminals listed as condenser, condenser fan, ground, and  wire #103 conds.  The dash air is not functioning now and it hasn't been for a few months. Don't know if this is related or not but thought I would mention it.

Will be checking wiring on #201 and #202 and determine power delivery to VIM today.

Thanks,


Tom

[Dave Atherton]

Tom, in beginning of problem you had motorhome at a Caterpillar Service shop. Cat tech
could not get any readout from data connector going to engine ECM and no start. You  mention
Tech than remove data cable from the J-1 connection on engine ECM and would start and run with
caterpillar breakout box
Same time you mention on ECM pin 70 which is the power and believe pin 51 & 53 are the grounds.
I do have the same breakout box that tech started your engine which will aid in finding your
no start problem. Retracing wires from wiring harness of J-1 will send you into a cat relay off
J-1 wiring harness to motorhome harness. This has a relay that been problemic and replaced with service bulletin update. Wiring harness off J-1 on ECM connects to that relay within 4' of engine
To motorhome wiring harness. Dave Atherton Retired Cat Mechanic