ScotW

I took my car in for service yesterday. My 2005 is getting about 1500-1800 miles per quart of oil (22,000 miles on odometer) and is on its second oil consumption test, after failing the first last year. In the service rightup the following comment was made:

"Found unkown program in PCM. Reset PCM to current management program. Tech case is open"

What gives? My car is 100% stock - well almost, I have replaced tires and don't even have a CAGS bypass. Advisor had no comment other that that's what they found. Never had the car tuned.

shopdog

The C6 doesn't have a PCM. It has an ECM, and if it is an automatic it also has a TCM, but no PCM. PCMs are only found on C5s and later production C4s.

gbgary

sounds like they're laying a foundation to deny some big warranty repair down the road. too bad.

Rowboat66

As a newb (bought my C6 last month) please explain to me what PCM and ECM are... I assume TCM is transmission control module, correct? Thanks in advance... I trying to absorb as much as I can quickly!

User 020720

Are you the original owner?

If not, the previous owner could have used a tuner or a handheld tuner like the Predator?

It's an 05, could it have had the DBS reflash? Just a few questions to consider.

johnodrake

Could be. I think I would not let this go....

Wayne O

I'm sure Shopdog is technically correct...his mechanical knowledge and expertise (on this forum) borders on legendary.

While the ECM may rightly be considered the 'control center' of the vehicle and there may no longer be a PCM per se, GM still makes reference to PCM with regard to the C6 (sometimes synonymously with ECM).

This is one reference...C6 DTC fault codes reference PCM as follows:

C0240 PCM Traction Control Not Allowed
C0242 PCM Indicated TCS Malfunction

This is an excerpt from a TSB concerning battery drain:

"...2005-2006. Finally if all the above information has been inspected and Strategy Based Diagnostics has been performed with no resolution, reprogram the PCM/ECM with the latest calibration through TIS-2WEB. Once the calibration has been down loaded to the PCM/ECM, release the vehicle for customer to evaluate...."

Apparently, PCM remains in the common vernacular by GM and others with respect to the C6.

phileaglesfan

I would defintely look into it since that comment can kill you on a warranty claim. If it is used, then they are probably right. I would want an explanation if it is new saying that my warranty is not void.

ScotW

Thanks for the responses.

I am the original owner. The base warantee expires in six days. I have a one year extended warantee. I have two major issues with the car that have gone unresolved. For someone who has been through unresolved warantee issues, what happens in this situation?

Issue #1. Oil consumption. I have had this problem since museum pickup three years ago. They have tied the unkown program in PCM to the oil consumption problem. I don't agree but that is what their documentation shows.

Issue #2. Engine Noise. With the car in neutral, reving the engine up slowing causes a shrill noise at 2800 rpm only when cold. When warm, the noise goes away. Reving the engine slightly faster from idle will cause the noise to appear at a higher rpm. On a previous visit, they determined the noise was from the rear of the engine, not any accessories. They replaced the bearings in the torque tube but the noise remained. Now the comments on the latest work order states "Unable to reproduce - working as designed".

What path should I follow to protect my warantee rights? Will the extended warantee protect me? The unkown program in PCM makes me nervous about their intentions. I have had no one except Mr. Goodwrench work on my car. The have scanned my car to determine my driving habits. The max RPM recorded was 4500 rpm. They say I should drive the car harder. Max speed in last 3 months was 55 mph. No way should I go through this much oil.

ScotW

I have never asked for the DBS reflash. If they did it, it was without telling me first or documenting it on the work order.

foremaw

If this dealer has had the car before, is it possible that one of their other techs tried (and maybe botched) an ECM programming for this or a TSB issue?

ScotW

I talked to the dealer today and he said they would have done the DBS reflash. He said it also may have come from the factory that way ?!!

I think your right, it must of happened during the DBS reflash.

shopdog

PCM = Powertrain Control Module, does not exist on C6
ECM = Engine Control Module, runs fuel injection and ignition on a C6.
TCM = Transmission Control Module, runs auto transmission.

shopdog

Just ask them for the part number for this C6 "PCM". They can't give you one, because no such module exists on the car. Unfortunately, GM's Tech writers are among the worst in the business. The number of obvious glaring errors in the shop manuals and owner's manuals is incredible. For example, the shop manual describes the headlights as biXenon with a mechanical shutter to switch between high and low beams. That is the system on the XLR, but it certainly isn't the system on a C6, as anyone who has seen the car could immediately tell.