Check Engine Light 300 hp cummins

[papooh]

We have a 2002 Bounder 39 R with a Cummins 300 and Allison 6 speed ~59K miles. we are getting an intermittent check engine light when idling or coasting downhill (but only with the exhaust brake off and foot off the throttle). It looses power when the check engine light is on.

Now whenever I start the engine, or let the rig idle after parking it the CEL will come on and when I start driving there is very little power for a few seconds. Then the light goes out and things run normally.

I took our rig to a cummings diesel shop today in St George, Utah and they hooked up their computer and said it was code 0368 - Engine power derate. But did not know what the problem was.

Any help would be very much appreciated.

Thank You,
Gary and Julie

[GaryKD]

Hi papooh,
Check your coolant level. Make sure it is well above the low coolant sensor.

[papooh]

Thank you very much - I check it and report back.

[EngineerMike]

The engine's computer derates or puts the motor in "limp mode" for one of two basic reasons, either there is a sensor input that is out of normal range to the point the programming doesn't apply, or a sensor is indicating a condition that would ruin the engine if run at full power. Low coolant is one reason, and a common problem, but other issues apply. If the shop has the proper software (and they know how to use it) they can read all the engine inputs (sensor levels) while the CEL is on, and should be able to spot the input that is causing limp mode. There may also be "freeze frame" data stored that would show the problem sensor input.

[ua40j]

Totally agree with Engineer Mike. Other things are oil pressure, exhaust manifold temperature, fuel pressure, etc.

Searching this forum, I saw several 'check engine light' issues with the ISB. One interesting common thread in the suggestions was checking the grounds on the engine. Have you had any electrical work done lately or had something unhooked and then reconnected? One of your sensors that impacts derate could have a bad or floating ground.

One thing I had early on in the life of my ISC was a loose connector to the fuel pump so I know it does happen.

I'm surprised the Cummins facility didn't find inactive fault codes for sensors that may have tripped. That could have been a big clue.

Good luck and let us know the resolution.

[J Walker]

I am suspicious of the shop that could not find a stored code that points to your problem. My Silverleaf VMSpc shows me a code for any fault that has happened in the past until I erase the code. I would get another check of the codes.

[a k]

Get someone with Cummis Insite and disable them limp modes. Don't need a limp mode for low cool level. Tow people like it.

[papooh]

I agree about going to a different shop. I scheduled a service appointment at the International truck dealer here in St George Utah for tomorrow morning. I'll post the results. Thank you all for your comments.
Gary Palmer

[a k]

Check this. If you could let me know what the serial # of the engine or the Serial of the ECM it would be easy to look it up and supply the fix. There's dozens of ISB combo engines. This is the only code for 368 that I found.

[a k]

Here's the fixit

[papooh]

You are correct - the Fuel lift pump is failing. The shop ordered the parts and they should be here tomorrow.
This is a costly repair. The lift pump is $1950 alone. It will be close to $3,000.00 total.
Thank you very much for all the comments and help with this.

Gary Palmer

[J Walker]

Gary
If it is the lift pump you are being way overcharged! The labor is also out of line.

[indiana journey]

Gary,
We had a new lift pump installed in our 2004 5.9/300 hp cummins 8/27/2007. The work was done at a cummins facility. The pump was $142.76 and the labor was $489.50 including a lot of diagnostic work. You might double-check the estimate for your problem.
Good Luck
Indiana Journey

[papooh]

Thank you for that information . We will look into it more before proceeding.
Thank you again.
Gary Palmer