SES light sometimes

[till]

The SES light will come on for a short time when I am towing. This seems to only happen on an up grade. I checked for codes and I get the Turbo waste gate error code. I do not have the number handy right now.
Is this going to be a really bad thing? I found that the mound for the solenoid mounting bracket is broken. I have used a tie wrap to hold it where it should be mounted. I am planing to checking the vacuum pump tonight.....

[JohnC]

Usually this indicates the PCM is unable to limit boost. It is generally caused by a sticky waste gate solenoid. Best to check the whole system before spending money, though.

[till]

The code is 78....

I have the books and followed the diagnostic chart to the...
"Refer to section 6J for further diagnostics"
I have about 22" Hg at the input to the solenoid.
I have 17" Hg at the actuator.
The air filter is about 6 mo old and still white.

The SES light was only coming on under heavy load on an upgrade. I get some black smoke and OK power.

I have noticed that I am starting to get the SES light now when I have a truck full of people.
My first thought at this point is to replace the fuel filter.

Thoughts.....

[JohnC]

Sounds like the wastegate solenoid is getting sluggish. If you have a scanner and monitor wastegate solenoid duty cycle, you will likely see it gradually get less and less and then, when the light comes on, drop to zero.

[till]

I guess than I will throw a solenoid at it. I am still on the learning curve with my truck.

Thank you.

[Kennedy]

Try a quick squirt of WD-40 in the vacuum tube at the actuator with the engine running. This helps the solenoid.

I've also seen this to be chip programming related. Been a long time, but had many complaints about this code as RPM crossed 2,000 and chip tuning generally cured it.

[till]

Heck I will try a squirt.

This seems to be a temp/load related problem. I had a chance to talk to the original owner and he mentioned that he would get the SES light on days when the temp was above 80 F under a moderate load, but could never get a code. He was not real specific about what type of load.

As I mentioned before, it seems to be with a full passenger count (not all adults) or with a trailer behind. And at that I have to be rolling and encounter a grade. The trailers are 5300 to 7000 lbs and the passenger load can not be more than 900 to 1000 lbs total.

The DCM is bone stock to the best of my knowledge. I am not sure if tuning would be an option at this point due to my limited experience with computer managed engines.

[JohnC]

This seems to be a temp/load related problem.

My experience is the solenoids first get flaky when they get hot. Also, below a certain fuel rate (load) the PCM doesn't monitor boost, so it won't set the code.

I stand by my original diagnosis!

;)

[till]

JohnC/Kennedy you are so right. I did the couple of squirts of WD and it cleared the problem for a short time. After the third time I just replaced the solenoid.
I am surprised at the power the truck has now. Now at 186K I believe that I need to save up for head gaskets from what I have been reading.......

Thank you for your input and patients.

Tedd