amfmlittle

iTrader: (1)

Hi People,

I am having some issues with my 2004 V. I was trying to reinstall the Superchips tune on it a few days ago and ended up with a "cannot communicate with the ECM" message on the Superchips tuner. A couple of minutes later, I got a "Service Theft System" message on the navigation screen.

I had a friend who works at GM plug in his Tech2 and clear faults, but had no results. I've disconnected the battery and ground out the vehicle (to eliminate all the current). I've also tried turning the key to the "on" position for 10 minutes, followed by off (cycled 3 times, as told by Onstar). Checked all fuses and have no issues.

Has anyone had this issue before? I'm thinking I have a bad ECM, but am looking for any other tricks or magic out there--maybe I need to open and close the door 4 times and clap and sing to it.

If I have a bad ECM, anyone have one that might work? Thank you!

MCasano1

Sounds like your ECM is shot. I use HP Tuners and smoked the ECM two times while reprogramming. It was my mistake because I was using "rewrite entire" instead of "rewrite calibration" while flashing the ECM. I ended up replacing the ECM both times.

Anyway, my ECM did the same thing you described and lost communication too, and I went through all of the steps that you listed. As I appreciate your post, the Tech2 couldn't connect either. If this is correct, your ECM is probably gone. Good luck!

amfmlittle

iTrader: (1)

MCasano1:

THANK YOU!

I appreciate the comfirmation....Time to get to work on this!

Happy New Year!

wait4me

iTrader: (10)

We have hundreds of those pcms in stock if you need one, they are 84 shipped to your door with a stock program in it for your vin.

STAGEUP

I dont think your PCM is fried. This happend to me a few times. What you need to do is upload the stock tune back in as a recovery. Once you do that, it will start right up!

MCasano1

I hope you're right, but if he can't communicate with the ECM there's no way to download anything.

amfmlittle

iTrader: (1)

I had also tried to go back to the original, but like MCasano1 said, I can't even get the thing to wake up. Any suggestions on getting my ECM to wake up? Thanks People!

STAGEUP

Yes, my pcm was doing the same thing. I kept trying over and over until it gave in! It took my like 6 tries.

amfmlittle

iTrader: (1)

So just keep trying? Interesting....

I'll give it a shot. At this point, I'm willing to do whatever before I start taking stuff apart. I think I've tried about 4 times so far.... A few more won't hurt.

Thanks!

wait4me

iTrader: (10)

IF the pcm failed during a full flash or if there was a data transfer error resulting in a checksum mismatch the pcm is more than likely dead and needs to be pulled apart and the flash needs pulled from the board and a correct bin put back in.

When you have that type of failure, the pcm just doesnt know what to do with itself so it just doesnt talk. Because it dont know how.

The new pcm types however have gotten around this major problem. To do that they now have a Boot flash meaning that no matter what you do to the main chip, it will always have its starting instructions for comms and other important functions.

But your pcm type does not have that safety yet.

Think of it as just like your home computer. if you put in a new hard drive with no software, your computer pretty much just sits there and doesnt do anything..
Once you put on windows or linyx then it can now "run its programs"

A502slo

iTrader: (4)

Well is the tech II can talk to it are we sure the PCM is done for??? Maybe there is a problem with your programer. Also does the car start?? What were you trying to do before you hooked up your programer? what changes did you make.

wait4me

iTrader: (10)

If the pcm is sending out messages then it is not done for and is recoverable with aftermarket software."most anyways" But if it is silent on the bus then it is for sure dead.

If the tech 2 will talk and identify it, sps should work but if it dont recieve a response the tech2 will fail..

STAGEUP

I was getting messages like "cannot locate VCM", and I got "Service theft system" on my nav screen. So I kept trying. I would wait about 2 min before each try, and then finally, it started a "recovery" upload. Car started right up. I then shut the car off, and uploaded my performance tune without issues.

These type of issues happen when you have either a bad interface cable, or USB cable. Or, it can also be a faulty USB port if you are using a laptop based tuner.

Hope this helps.

amfmlittle

iTrader: (1)

Hey guys,

When my PCM shut down, I was trying to reinstall my performance tune in it. I had done it before with no issues. This time around, I got a message "cannot communicate with ECM" and then I got the "service theft system" message on the nav.

I know some friends that work at GM and they brought the engineering version of the TECH II. No matter what we did, we couldn't establish communication with the pcm.

Does this clear up some questions? Thanks a TON for all your help so far...

As of now, the car's in storage for the winter anyway. I'm going to remove the PCM soon and see if I need a replacement. Any suggestions?

MCasano1

From my experience, it's fried. But, STAGEUP saved his from the dead somehow. For $84.00 shipped to your door from EFILive, life is too short to mess with that one. I'd just get a new one and be done with it.

2c5s

iTrader: (11)

Will they put the vin on it? If not, another $92 from the dealer.

MCasano1

I guess so - this was his post from earlier in this thread.

STAGEUP

Im starting to think I got lucky! Haaaa!

amfmlittle

iTrader: (1)

I'm ordering wait4me's ecu. I hope that covers all the issues and I can get my car started soon! Thank you for all your help with this...

I have one more question....when I install this ECM, any words of wisdom I need so I don't blow this thing again? I'm going to plug it all back in and reflash the performance tune (my superchips). That all it?

Thanks!

amfmlittle

iTrader: (1)

I just wanted to to give a public THANK YOU to wait4me. My car is back up and running!

Thanks to everyone who gave me advice!