04.5 Duramax LLY getting p0101

[D2theMax]

I'm really hoping to get the help I need here. The problem I'm having is recently when I drive my truck into work which is an hour away, when I come to a stop I go into Limp Mode. I have an Edge programer so I looked at the codes, I'm getting a p0101. My air filter is about a month old and it was clean. I used some MAF Sensor cleaner really good, and put it back on. I start it up and get to driving and when I come to a stop at a light, it goes into Limp Mode. I used to be able to shut my truck off for a minute or two, clear the codes and away I'd go, but it's getting worse. Here's some things I've taken note of, My Vanes usually at idle, are closed to about 88-89%. Since my p0101 issues, I've noticed when I come to a stop my Vanes drop to 0% and stay for a while, then fluctuate and my MAF g/s goes from 30-40 down to 17 g/s when that happens. I came to work this morning and decided to give it a little gas when I had to stop at a light, keeping it under load. My truck didn't go into Limp Mode when I did that. Can anyone help me troubleshoot this one so I don't go and dump a bunch of money on a new MAF Sensor or Turbo rebuild kits, or the hundred other things it could be? Thanks in advance!

-Brad

 

[Lparrill]

I would get some electrical cleaner and make sure the connections are clean. I would also take apart the bail connectors on drivers side valve cover and use electrical cleaner on that. I had a similar issue (though mine was cam position sensor/accelerator pedal) that cleaning the bail connectors fixed it.

IIRC correctly (hopefully someone with more diagnostic knowledge can confirm or debunk this) but I think the MAF and vane position sensor are on the same circuit.

Also, it should be said to check out the wiring that goes over the alternator bracket. LLY's have a tenancy to rub through the harness in that spot.

 

[D2theMax]

I will go back over the connections with electrical cleaner in the a.m. I'll probably switch out the air filter just to rule that one out too. The guy I bought my truck from a few months back did a Kennedy air box mod, if you think that could be an issue?

Also good call on the wiring going over the alternator bracket, I didn't think to even check that.

Would you happen to know why if I turn my truck off for a good 10-15 min and clear the code, it's like nothing ever happened. No limp mode and I can drive an hour and it might not even throw another code for a few days? It's odd to me.

 

[gmduramax]

EGR?

 

[2004LB7]

Stock air filter or aftermarket?

 

[D2theMax]

EGR?

I thought about this as well, but I can hear my EGR valve closing and opening still. My turbo tho, no longer spins up, but I'm not sure if that's something that's disabled when in Limp Mode.

 

[D2theMax]

Stock air filter or aftermarket?

Stock Air Filter, however, the guy that owned it before did something called a kennedy air box mod. Basically he knocked a large chunk of plastic off the front of the box allowing more air to enter just below the filter. I am also running an STP paper filter and not the OEM AC Delco brand they recommend.

 

[KyleC4]

Just remember egr is a stepper motor and not directly connected to the egr valve. the stepper motor can move properly but it’s possible for the egr valve to get hung up. Especially from open to close

 

[D2theMax]

Just remember egr is a stepper motor and not directly connected to the egr valve. the stepper motor can move properly but it’s possible for the egr valve to get hung up. Especially from open to close

What is it that I hear when sitting at idle and my exhaust changes from sounding throaty to sounding restricted, back and forth? Isn’t that the egr opening and closing?
If I’m going to remove and clean the egr would you recommend just blocking it?

 

[2004LB7]

That would be the turbo vanes. They cycle to help prevent them getting stuck

 

[D2theMax]

Update: so while I was in limp mode I grabbed the wires that were bundled above the alternator and “click!” Some loud click noise and it took itself out of limp mode which it has yet to do before. I haven’t been able to limp it since?

 

[Lparrill]

Update: so while I was in limp mode I grabbed the wires that were bundled above the alternator and “click!” Some loud click noise and it took itself out of limp mode which it has yet to do before. I haven’t been able to limp it since?

Sounds like you need to inspect that harness more. The harness rubbing on the alternator bracket is a typical LLY problem causer.

 

[KyleC4]

Wiring repairs definitely easier on the wallet than hard parts. After you do the repair get a piece of dense 1/2 thick adhesive backed foam and put over that alternator bracket and then zip tie harness just snug to it.

 

[D2theMax]

Whoever here guessed a stuck open EGR, you would be correct. I took it off and it was caked with soot. I pushed on the valve and it just stayed open. I hit it with a lot of carb cleaner and cleaned it out. No limp mode and no codes. It was odd to me that all I got was a p0101 for MAF sensor.... thanks for your help fellas.

 

[Chevy1925]

Whoever here guessed a stuck open EGR, you would be correct. I took it off and it was caked with soot. I pushed on the valve and it just stayed open. I hit it with a lot of carb cleaner and cleaned it out. No limp mode and no codes. It was odd to me that all I got was a p0101 for MAF sensor.... thanks for your help fellas.

it may come back. if it does, you need to check the wiring bundle you grabbed on the alt bracket.