Took my car to get tuned on Wednesday and a couple days later we've made 2 baseline dyno pulls and spent the rest of the time troubleshooting . Car is a '99 C5, using HPTuners Pro, downloaded the latest software.

When you plug the cable in, it shows it getting power like normal, but the busy light starts flashing. Whenever we would try to flash the PCM or scan, it throws an error saying "Unable to locate VCM. Verify cable is connected and key is in the RUN position"

It connected and flashed one time, then would not connect again. He grabbed a friends laptop, installed HPTuners on it and it allowed it to flash one time then would not connect again. Tried uninstalling/reinstalling software on the laptop to see if it was software based and it made no difference. These two times it worked seem kind of like a fluke. It never lost the connection like I have read some people have had issues with, but it would not connect again.

Also tried disconnecting the battery several times to clear things out, to no avail.

Ran through some stuff with the HPTuners support people, they concluded it was the cable. But the cable was verified to work fine, he tuned a few other cars with it yesterday.

I pulled the PCM out and he bench flashed it, which worked fine.

The BCM was swapped in 2009 and never performed a relearn. While I have heard of this causing problems, the car has had no issues from that and has been tuned several times (using HPTuners) since then without any issues.

I pulled all the standard fuses (didn't pull the maxi fuses, pulled all of them from both the interior and under hood panels) one by one to see if killing power to a module or the BCM would possibly help, no change. The cable kept flashing busy. We were thinking there may be a data stream running to the PCM from another module in the car keeping it busy, but if that is the case we're not sure what it is as the fuses made no difference (besides one that killed power entirely).

The OBD2 port seems to work alright, the car can communicate to a normal 'dumb' OBD2 code scanner without issue.

We're both kind of at a loss right now and not sure exactly how to proceed. He thinks that the dealer may be able to run diagnostics to check the status of all the modules in the car. Would a dealer have anything besides a Tech2? We can get a Tech2 if it can provide any useful information. Either way, I need some direction as to what to even look for (or tell the dealer to look for...)

Any suggestions or help would be greatly appreciated...I've been searching and reading but haven't quite found the same situation, I'm hoping someone has run into similar issues before and can steer us in the right direction.

 

I get the same thing occasionally with my car. I just unplug the cable at the USB port on the laptop, plug it back in, and it always works.

 

Thanks for the reply!

He unplugged and replugged it so many times I'm surprised the cable still has ends attached to it.

Also tried 'leaning' the cable over at the ALDL port/pulling it over to the side a little, no dice there.

 

yea have to unplug both ends of the interface

 

You are not alone with that issues. I unplug the cable at the USB port on the laptop plug it back in and it usually works but not all ways.

 

Any other ideas? Kind of at a loss here, I'm going to start tracing out wires tomorrow if nobody can come up with anything else to try.

 

Check to make sure the pins in the OBD2 are in tact and grounds and +12V are working correctly.

 

I have the same problem, if I shake the interface and plug back in it sometimes works. It's a big problem when I'm logging because when I hit a bump it losses connection.

 

When this issue occurs I unistall and reinstall the A/B USB drivers. Works for me!