Electrical Grimlins or Something Else?

[amc019]

Had a few issues come up with my truck over the past couple weeks and I am struggling to figure out what the root of the problem may be, and the dealer seems to share similar difficulties.

 

All of this started out with a Check Engine Light that appeared randomly after it struggled to start up once, and when I say struggle, it just turned over more times than it usually takes to fire up. OnStar stated that the code was reading low voltage in one of the sensors on the fuel system, she was not entirely descriptive. Took it to the guy that tuned my truck with an HP Tuners tune, and he found a P0641 trouble code, showing an issue with the 5V Reference Voltage for sensors within the motor. The truck was also throwing a code (cant remember which) for faulty or incorrect barometric pressure readings within the intake manifold. After awhile, the trucks condition worsened, where every time I needed to apply a heavy amount of throttle from a stop or extremely slow start, the truck would cut out, almost like it was starved for fuel or hit the rev limiter, and kind of hiccup until it got rolling. It does not do this once the truck is moving at a fairly quick speed, like passing cars on the highway it doesn't miss a beat.

 

I had my tune removed from the truck and set back at stock, and took the truck to my local dealer. They decided that the truck needed a new ECM and replaced it under warranty. Great. Engine light off for 4 days and came back on after I applied heavy throttle from a stop to get around another car where the truck hiccuped like it had before. The following weekend, I was towing my side by side on an 18ft car hauler for the last weekend of duck season, and the truck really struggled off the line while under load, I had to ease it very carefully from a stop to prevent it from hiccuping and cutting out, not giving it much throttle at all.

 

So yesterday I brought the truck back to the same dealer, and they decided it was the Mass Airflow Sensor, replaced it this morning and by the time I got home I managed to get the CEL to come back on and do the same thing it had been doing before.

 

The only other issue with the truck occurs when I go to fill up the fuel tank, something happens where the pump almost always thinks its full, and cuts the pump off. I am assuming it is a bad vent solenoid, or the charcoal canister, but that issue has taken a back seat to my current issue. It has been like that long before any other problems occurred, so I am assuming that the issues are unrelated. (unsure of technical term for the solenoid or if they even use charcoal canisters on these trucks anymore) Other than that, the only codes popping up are for my HID headlights, the truck thinks they're burnt out or faulty, but these codes alone do not cause the CEL to light up.

 

However, it is possible in my mind that something is occurring in the gas tank that is not allowing it to vent properly, and under heavy loads where more throttle is applied and large volumes of fuel are needed, maybe the tank is starving the motor? Which causes it to cut out momentarily. Kind of like pouring gas out of can without the vent opened up, just tries to suck the sides of the jug in and doesn't allow good flow. I am just throwing shit at the wall and hoping it sticks at this point.

 

I take the truck back in tomorrow to see what the dealer can figure out. I hope someone can give me some advice as to what the issue could be, as I am getting annoyed with taking so many trips to the dealer. Thanks in advance.

[pm26]

It seems that your truck is suffering from "We flushed the quality control down the toilet" gremlin.

 

 

Systematically check all your electrical connectors to various sensors. Do this after disconnecting the battery negative terminal cable. I would unplug each connector, check that it is free of corrosion and plug it back.

[amc019]

You could be right, I had a 2011 Duramax before this, and had many issues with it as well. I really thought I would be doing myself a favor by going with a 1/2 ton this time around to avoid issues like these, but apparently not. I am a GM guy at heart, this is my 4th GM truck and I am only 22, but it seems like I have the worst luck with them.

[newdude]

Just make sure they don't find these as the cause:

 

2015 GMC Sierra All-Terrain Crew Cab

6.2 & 8 Speed - 2.5" CCM Level - 305/55/R20 MTZ - AirAid CAI - Magnaflow-HP Tuners

 

Took it to the guy that tuned my truck with an HP Tuners tune

 

 

If they do...bye bye powertrain warranty...

[amc019]

Just make sure they don't find these as the cause:

 

 

If they do...bye bye powertrain warranty...

 

They haven't said anything about the tune, as I had it cleared and set back to stock before taking it to the dealer. Some say they are traceable, some say they aren't, who knows. The tech that has been working on my truck mentioned that his supervisor questioned the intake, but even the tech told me that he has one on his truck as well and not to worry about it. Either way, the dealer would have to prove that the intake single handedly caused the malfunction in order to void the entire warranty. I think if they wanted to void it they would have by now, its been in their hands 4 times so far.

 

Also, I've had the intake on the truck for almost 6 months, if that were the culprit I believe the MAFS would be the only thing it could affect, and even a once they installed brand new one it didnt fix my issues.

 

At the same time, I have never heard anyone mention that a custom tune caused a problem with the electrical system on their truck. The guy that did mine builds racing corvettes, trans am's, and everything GM related, so I am confident in his abilities as a tuner.

[JimCost2014]

here is a thought. have them check your battery. if the battery is going bad, it can send a low voltage signal that will "throw codes". some can be read, some can not. just had my battery replaced because of the low voltage signal, I was getting "service brake assist" and "service stabiltrak" with out any codes to show why. good luck!