check engine light again - different cause

[Stan Simpson]

We just returned home from a 105 day, 4000 mile, trip exploring Florida. As we left Perry GA, my check engine light came on sporadically, especially when pulling a grade. The light went off as soon as we leveled off or were going downhill.

The nearest CAT dealer on our route that had the ability to plug in to the EMC was in Chattanooga. Stowers Machinery diagnosed a failed boost pressure sensor, and $574.00 later we were on our way.

Two years ago, we had a different sensor cause the same symptom. Intermittent check engine light. Wondering if there is a root cause or just wear & tear. We passed 70,000 on the odometer during this last journey.

[Gerald Farris]

Stan,
Assuming that you are not getting water intrusion at the sensor wiring connectors from pressure washing your engine, there should be no common cause for the failure of two different sensors on your engine.

Later model engines have narrowed the parameters for setting a "check engine lite" in an effort to reduce emissions, and this causes a few more occurrences, but the sensors are normally very dependable. My coach has never had a sensor failure, and it is 16 years old with 160,000 miles.

Garald   

[Dale Soule]

check engine light has sporadically come on our C-9 sometimes solid or a soft blink.  15 min every hour, I keep the r.p.m.s up on hills, does not seem to make a difference.   The engine does not seem to derate in power which the Cat manual mentions.   A gentleman in the park at Mesquite has a C-9 in a different coach, had this happen.  Said it was a barometric pressure sender, Cat did not have the part & left. How serious is this?  (barometric sender).   

[Dave Atherton]

Stan, maybe I can shed some light on you question. There is a group of sensors that are
5 volt and are all connected together in a group that sends a value to the ECM via: signal
wire. 161-170 Atmosphere pressure sensor, 161-1704 Boost pressure sensor, 161-1705
fuel pressure sensor. The 161-1703 atmosphere and the 161-1704 boost pressure sensor
are very similar and most common to fail in this 5 volt sensor group. One thing that is most
over looked when replacement of the 161-1704 boost pressure sensor is the boost pressure
regulator. 230-9944 which is on the left side of engine in back about middle of engine block.
The boost pressure regulator 230-9944  will generate a code 102-7 which is mechanical and not
responding, or 32-05 low current or 32-06 high current in 161-1704 boost pressure sensor
and is a electrical problem. Most cases, both sensors and the regulator are changed at same time.
Look at your billing cost should be !61-1704 boost pressure sensor $ 140. 00, boost pressure
regulator 230-9944 cost $ 259.00. Dave Atherton Retired Cat Mechanic

[Stan Simpson]

Dave,

Could you run the specs on my engine, please?

Serial #9DG04119

Thank you,

Stan

[Dave Atherton]

Stan, Cat C-9  9DG04112, A/R number 249-8410, 400 hP, Speed 2100 rpm, Adj Boost
32.7 psi, fuel pressure 80 psi, oil pressure 50.3 psi, fuel rate 15.8 GAL/HR, TQ Ck Speed
1400 rpm, peck TQ 1100 ft lbs, low speed 700 rpm, low oil pressure 21.7 psi., intake
manifold temp 120 DEG, Inlet air temp. 122 DEG. Dave Atherton Retired Cat Mechanic

[Stan Simpson]

Thank you, Dave. Your reply shows a different engine Ser# than what mine is.

[Dave Atherton]

Stan, engine build numbers do not come 12345 etc. listing engine build,  each engine will
fall into a list of numbers than will assign a arrangement number to that list. Than the
spec's engine testing will be used again for engines in this list. They do not just make a
set of operation spec's just for your engine only. The above information is correct for
your engine build. Dave Atherton Retired Cat Mechanic

[Dale Soule]

Dave & Stan:  how serious is it if these sensors are not fixed right away? Fuel mileage, exhaust, engine damage, or performance.   I'm thinking 1500 miles till I can be near a Cat Dealer.

[Stan Simpson]

I first noticed the light come on when we left Perry, GA. I tried two Yancey Brothers' shops in the Atlanta area, and neither could hook to my diagnostic plug. Tried another in Calhoun, GA and they couldn't either. Eventually found Stowers Machinery (Cat Truck Dealer) in Chattanooga, and they were able to diagnose. So I drove about 225 miles (with an overnight stop in between) with the light going on and off.

I checked all fluids, and felt I was safe as long as they were okay with no leaks, and oil pressure and heat gauges were in range.

[Dave Atherton]

Stan, will you be at FMCA At Perry or Rayne, LA.  If so I do have Cat ET engine computer
with us and give assist in your problem. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Hi Dale, what you have happening with light on & off is an Event Code. This means that something
Is happening like a short, dirty connection etc that causing your blood pressure to raise, than light
Go off like nothing happens and you keep going. Why because an event code resets itself and
will log on ECM an event code when you have Cat put Cat ET computer on engine. Just possible
when was the last time you changed your secondary fuel filter, reason if secondary fuel filter is
getting filled with diesel fuel fines and reach a 7to 10 psi your check engine light will trip
On and off. At 10 psi as pressure rises or filter is getting filled with fines, light will stay on at first
Than will start blinking than engine will lose power to 1100 rpm or called Derate and will only
Reset itself when secondary fuel filter is changed. ( this is only if you have a Cat secondary
fuel filter, if you do not have a Cat fuel filter you ECM protection is removed ). A person can
have to change a fuel filter today within day after service because diesel fuel today is not
So good at some fuel stations.  I would start at this point first
Dave Atherton Retired Cat Mechanic

[Dale Soule]

Dave;  Thank you.  Changed both filters August 2015 The glass bowl looks clean, maybe 2,000 miles tops.  I have read the blogs on fuel filters.  The Shop put a Cat 1R0751 and a NAPA Gold 3231 with a glass bowl & drain.  This will be changed when I have time.  Will the Cat filter work on this arrangement?   I will start with a Cat filter if it will mate up with what I have.  Is this a serious problem with engine light working sporadically? Say 1,500 miles.+/-

[Dave Atherton]

Dale, do not worry about the light going on than off your not going to damage anything. I
again would look at the fuel filter first 1R-0751 ( do the easy things first ). Second possibly
Boost pressure regulator 230-9944 ( read post, boost pressure sensor for Cat C-12 ) what
may be happening boost pressure regulator sticking off and on triggering light on dash.
Cat ET code will be 102-07 boost pressure regulator. The way it appears you are not in trouble.
Driving keep watch on your boost pressure gauge, under load your boost max pressure
should be 32 psi. Starting and standing still at idle boost pressure should read zero.
Dave Atherton retired Cat mechanic

[Stan Simpson]

Dave, no I won't be in Perry for the FMCA. We stayed there for one night on our way home from Florida.