2005 M1088a1 C7 check engine and deregulating at 40 mph

[Cgray]

Went through days of reading archives threads and tons of pages of current threads.

I feel like I have done due diligence before asking any questions about the issue.

Truck has run run great for last 10k miles at highway speeds and towing 5th wheel. Now after some -30* weather the truck is having some electrical issues. I did replace the batteries and have good charge.

When I hit 38-40 the truck check engine light comes on and the truck seems to “limp” at a sustained 40 or less. Sometimes it almost feels like the turbo is failing.

I checked the alternator and on the 14V side I am getting a yellow intermittent LED flash and sometimes a red.

Any suggestions ?

 

[snowtrac nome]

the c-7 is an electronic engine you will need a scan tool to pull codes the cat dealer will use cat e-t prolink makes a scan tool that will access the engine if yours is an acert engine. now days I just use the laptop with e-t once you get the codes than we can go from there doing diagnostics. Not knowing what year yours is its a good bet you have an exhaust related issue. get codes and I can help. The esn would be a big help to determine what emission's system you have. one problem we have had up here is with exhaust after treatment systems not working correctly because you can never get the engine to warm up properly with no highways and stop and go around town driving. another common problem I have seem is mufflers plugging with a tar type substance.

 

[snowtrac nome]

I should also add the tcm and ecm talk to each other and the transmission could be throwing the code.

 

[Suprman]

If you have a charge/low voltage situation that would cause all kinds of issues. Can you measure your running voltage outputs? A standard heavy duty truck code reader will pull codes. Have you checked all your battery and power connections?

 

[Cgray]

Snowtrac,

Its a 2005 C7 ACERT.

What possible exhaust issues could cause something similar?

Superman,

Checked all connections. Replaced one battery terminal because it seemed a bit loose.

I did find a solenoid type connector on driver side near the starting fluid tank on rear of engine. It has rubber grommet type mounts and is some sort of battery related part. It slid out of the mount but all the cables seem tightly connected. Will disconnect them tomorrow and sand with plumbers tape and use dielectric to reassemble.

Checked batteries disconnected from truck:

12.5 V disconnected each

with truck running:

27-28 V on 24V side

12.6-13.08 on 12V side

With battery disconnect switch engaged:

alternator LEDs flash red and yellow

 

[Ronmar]

Was that voltage AT the batteries? 12.6-13.8 on the 12V side is low, should be 14.5, or at the very least 1/2 of the 24V side, which in a perfect world would be closer to 29V... this could be as simple as a poor connection between alt and battery. A quick check is to measure the running voltages at the alternator 12 and 24V terminals...

engine is computer controlled, you need codes to effectively troubleshoot it...

 

[Cgray]

Ronmar,

I will run the voltage of the alternator in the AM and report back. I ran check on battery side of cables.

 

[snowtrac nome]

In the commercial world the 05 acert engines had a catalyst in the muffler it made them real expensive but were also prone to plugging up especially if not driven at highway speeds to warm up egt's. I have also seen around here standard mufflers coke up with a tar looking substance again from the lack of highway driving and extreme cold temps.
the coking is not limited to cat engines I have seen it on all of them cat Cummins Isuzu mechanical and electronic injection.

 

[Cgray]

PROBLEM SOLVED:


The issue wasn’t throwing codes. Just a check engine light and deregulating at 40-50 and wouldn’t increase.


After reading civilian threads on the C7 and YouTube videos I deduced that it could possibly be low fuel flow. Possibly a clogged filter.


I replaced both filters (RACOR R45P / CAT IR-0751) and the engine is back to running normal. I initially had a feeling that it was possibly a loss of turbo pressure but that was just a loss of power due to starving the engine of fuel pressure.


I guess the lesson learned here is to have a better 3M / PMS schedule. I never would have thought the fuel I have been purchasing would be dirty. However the RACOR filter stated otherwise with all of the debris in it.


Thank you to all that helped troubleshoot the issue.

 

[Ronmar]

Cold could have had something to do with it also... you said you had alternator lights flashing, and y0ur voltages didnt sound right...

 

[Cgray]

So I haven’t figured out the voltage issue yet. Still working it. I did drive 370 miles pulling the fifth wheel Friday and it did great.