Major Electrical and Module Issues - Help!

[bobang]

I have an issue with my 2007 ½ GMC Sierra 2500HD LMM truck, that I really need so experienced help understanding. My truck has 150,000 on it and has never been in the shop. I put an H&S Mini Maxx tuner on it, in 2011, after removing the DPF and exhaust from the turbo back. Everything ran great until 3 weeks ago.

 

I was driving to work and the check engine light came on. I checked the code and the DTC code was “PO642 Sensor Reference Voltage A Circuit Low”, but the truck was running fine. I did some research and discovered it was this could mean the crankshaft sensor is bad. No big deal. I when to NAPA and bought another and installed it. Tried to clear the code and it came right back seconds after clearing it.

 

Did a little more research and discovered it could be a Fuel Rail Pressure Sensor. However, this is too expensive to replace without being sure, so I called my local Chevy dealer and asked him if he could trace the DTC code to the sensor and avoid me randomly replacing stuff. He said yes, should only take an hour and $130.00 so I set up an appointment for Thursday of that week.

 

On Sunday, prior to the appointment, I had the truck warming up in the driveway, when I noticed it stopped running. I tried to restart it and it would not start. I checked the fuel and there was fuel I the fuel filter. I had to run to an appointment, so I took my wife’s car. When I returned, the truck started right up. Strange, it will start when it’s cold, but not warm. I duplicated this several times and never saw any new DTC codes. I decided to have it towed to the dealership.

 

It sat there until the scheduled Thursday appointment. The service rep called me and said there is a short somewhere in the wiring harness and three sensors that would produce that code and it could take up to 10 hours to find it. He also said the battery was completely dead and they had to push the truck into the shop. I authorized the work. The next day he said the ECM was bad and was causing the low voltage issue. I authorized a rebuild ECM. He later called me and said the tech could not communicate with the ECM through the ODBII port and the truck would not start. He plugged in the old ECM and couldn’t see it either. I went down to the shop and confirmed that my Mini Maxx cold not see the ECM either. Strange

 

After doing more work, he determined that the Glow Plug Module had power going to it, but nothing after it and that the module was bad. Strange, I’ve never had a glow plug issue or fault. They replaced that, and still couldn’t see the ECM or start the truck. After more work, he unplugged the Mass Airflow Sensor and could now see the new and old ECM, no error codes in the new one, and the truck starts. Plugs the MAS back in and the error code appears and the truck won’t start. So now he has a new MAS on order.

 

He stated that the bad MAS could have taken out the Glow Plug Module and the ECM. Does this make sense to anyone, because it makes no sense to me? Did he do something that could have caused all these modules to blow?

[Heavy 5.7]

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[SpartanAutoworx]

Im sure both the old modules are good. I would only be paying for the MAF as they mis diagnosed the other two issues.

[Justin101714]

No sensor is going to take out any module.....NEVER!!! They scammed you. World Class GM tech here and have heard this same kind of crap for many years by technicians that are brainwashed by other techs that don't know what they are talking about. Go talk to the service manager and demand your money back, if he/she doesn't help, find the general manager.

 

 

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[bobang]

Justin, from the research I've done, I agree with what you are saying. I went into the dealership on Wednesday, after they installed the MAS, and the truck started fine. I reinstalled my tune (I have no DPF on my truck) and took it for a drive. Everything ran fine, no codes. Went back into the dealership and met with the service manage. The total bill was $4500 and I have an additional bill of $500 for three weeks on the rental car. After arguing with her for 30 minutes, she knocked the bill down to $3000. I had to pay it to get my car back. I did request the parts replaced be returned to me, in writing, per Washington State law. However, when I returned home, I realized they never gave me the parts.

 

The question is, what to do now. I could request a meet with the GM and tell him if him I'm willing to pay for the MAS and three hours of diagnostic time, but that's all and asked for a refund of the request of the money, plus they pay my rental car bill. If they don't comply, my only leverage would be to file suit in small claims court. However, I would need to have an expert witness testify they are full of crap. They second challenge is the fact I don't have a DPF on the truck. Could they turn me in for that?

[Justin101714]

Well, I've seen this type of scenario plenty of times. Just show up at the location and asked to speak with the general manager. Don't call anyone, just show up. They hate that most [emoji23]. Explain the situation, every dealership has what's called a CEM or a customer experience manager, you could speak to both. Tell them your issue, bring any and all documentation of repairs and while you're there, get the old parts back. The only next step would be this. Demand your money back, no asking here! I'd be pissed!

 

 

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[Coby7]

Remind me not to go to that dealer.

[bobang]

Thanks. I'll go in on Wednesday and do that.