After 2 weeks at the dealer, I got my truck back Tuesday with 8 new injectors. I drive her back from the lake tonight (Sunday) and the SES light pops up and tranny does not want to shift (holding back at 1800 rpm). Is this limp mode? Anyone else have this problem and might know the cause? I have no chips, stock exhaust, and only "mod" is K&N. Changed fuel filter 2K ago. Thanks.

Sounds like Limp mode - if it is, it will start up in 3rd gear and won't shift - if it is, you should be able turn the truck off and let it sit for a few minutes and restart and it will go back to normal. Were you towing? Hitting it hard?

I have been going thru all the same things that you are going thru. Last year I had my injector replaced and this year it started it again. Now, The first thing you need to do is replace the filter. After that, who knows? When mine did it this year I carried it ot the dealer and they said it was the Fuel Pressure Regulator, they wanted $852 to repair. I ordered it for $200 and replaced it myself. Guess what? That wasn't the problem because mine is still doing it. Good luck!

It appears we have about the same truck. Here's a little advice... Service your transfer case!!!

Sounds like Limp mode - if it is, it will start up in 3rd gear and won't shift - if it is, you should be able turn the truck off and let it sit for a few minutes and restart and it will go back to normal. Were you towing? Hitting it hard?

1800rpm limit is not a trans limp ;)

Sounds like the way mine acts when I don't change the fuel filter like I should. When's the last time you cleaned your K&N? Fuel filter's can clog on one tank of fuel too.

It appears we have about the same truck. Here's a little advice... Service your transfer case!!!


This has nothing to do with your truck limping. just some free advice :)

Sounds like Limp mode - if it is, it will start up in 3rd gear and won't shift - if it is, you should be able turn the truck off and let it sit for a few minutes and restart and it will go back to normal. Were you towing? Hitting it hard?

I had towed earlier but not when the SES came on, I was just going up a slight grade.

3 days ago the SES fairy came and took away the light and the truck ran normal. Yesterday she revisited and brought the SES back with all the symptoms of before. When I shut the truck off last night SES was on, I started it this morning (stayed on) and drove to work with it on and no limp mode. I started the truck back up about 10 mins after work and no SES anymore. This is some strange behavior. Any ideas?

I would check the codes. Sounds like the most recent service bulletin on fuel system. SES automatically goes off after so many starts if problem clears, which may be the p0093(fuel leak) or the p0087 (which is misfire). Does it downshift alright? Mine did the same thing going up a grade towing, and eventually wouldn't even carry itself up an on-ramp. Turned out to be injectors, but I think it could possibly be the cp3 injector pump. I would start with a new filter, and go from there. GM might have put some bad injectors in, just a thought. Good Luck.

1800rpm limit is not a trans limp ;)
What's the tranny limp, 2000?

I started the truck back up about 10 mins after work and no SES anymore. This is some strange behavior. Any ideas?Trans limp mode will leave the SES light on for a couple days I think, so probably not that - like mentioned, go to autozone etc and get a code reader and find out what codes are set is the best next step.

I would check the codes. Sounds like the most recent service bulletin on fuel system. SES automatically goes off after so many starts if problem clears, which may be the p0093(fuel leak) or the p0087 (which is misfire). Does it downshift alright? Mine did the same thing going up a grade towing, and eventually wouldn't even carry itself up an on-ramp. Turned out to be injectors, but I think it could possibly be the cp3 injector pump. I would start with a new filter, and go from there. GM might have put some bad injectors in, just a thought. Good Luck.

Truck downshifts fine so I hope I can write off a stubborn allison. I have read about the C3PO pump being an issue worth pursuing ($800 fix at dealer). Anybody know what it takes to install a new cp3 pump, what the pump does, and where to order?

I've driven her 3 days now with no problem. Do you know if the codes stay in the diagnostic computer after SES light goes away or does the SES have to be on when you check the codes?

Time to call in R2D2?

The engine computer will keep a history of any trouble codes that have been set. A scanner can pull up any codes in the ecm. Can also be done with a tech 2 or some aftermarket programmers.

most parts stores will read the codes for free. It sounds a lot like what I am going thru. I wish you luck. I have had mine checked and it was supposed to be regulator so I replaced it.... no luck!!! now I don't know where to go next. I think the next thing is the pump. I have asked if the sensor could be bad and no one has answered that one.
Again, good luck!

Could be your NBSU switch.

Problem: P0093 Fuel Leak (Large).

Back to the dealer? What gives?

Sounds like a new cp3 is comin' yout way.

What

Could be your NBSU switch.

What is NBSU? that causes a LIMP p0093 code?

Could be your NBSU switch.

Neutral Back Up Safety Switch. It goes and you tranny does not want to shift. I did not see that you threw a P0093. Could be your CP3...like said above.

Look up the special policy here for p0093. Has to do with return rates and a couple different codes, but thats one of them. Hope it's not the fuel pump, good luck.