Damnedest car/problem?

[Bruce Melton]

So I am trying to tune this lightly modded 03 C5 A4. Stock OS, PCM etc. OS>12221588
Spent about 10 hours trying to get repeatable hookups to V1 and V2.

In the end it will not scan with V7.4 xx. It locks up and tach reads 3745 rpm. Only thing on dash (any dash, including default) that works is PLX WB gauge. So I use another laptop with an old 7.3 which works fine. To add insult it will not tune with 7.3 but will, normally, with 7.4!

What have I tried? You name it?
7.4 early and late versions work fine on my car and others.
Today was typical for this car, I had to use the two- 7.3 and 7.4 to scan/tune- then went over to my car running 02 OS and 7.4 worked normally both V1 and V2 scan and tune.
I have properties properly addressed I believe, and I have borrowed a third C5 and used four laptops with consistent results. Three different weeks no problems in between.

Am I losing it, or does someone have an idea?:Eyecrazy:

[dfe1]

This is going to sound like a statement/question of the obvious, but have you considered swapping PCM's? If the software/laptop combination you're using works on a number of other vehicles, then as you've noted it's obviously a vehicle specific problem. Corvettes can be a real problem because of the interplay between all the different modules. You might find that a Tech 2 will pinpoint the problem fairly quickly. If that isn't an option, you may have to swap out suspected components until the culprit is found. If you have a spare PCM laying around, start with that. I've seen cases where the PCM was bad, but no codes were set. Good luck-- hope this helps.

[Bruce Melton]

This is going to sound like a statement/question of the obvious, but have you considered swapping PCM's? If the software/laptop combination you're using works on a number of other vehicles, then as you've noted it's obviously a vehicle specific problem. Corvettes can be a real problem because of the interplay between all the different modules. You might find that a Tech 2 will pinpoint the problem fairly quickly. If that isn't an option, you may have to swap out suspected components until the culprit is found. If you have a spare PCM laying around, start with that. I've seen cases where the PCM was bad, but no codes were set. Good luck-- hope this helps.

Yes, what you say seems obvious, and I suppose the obvious solution is to swap the PCM, but I wonder what it is that lets V7.3xx hook up and 7.4.xx not (scan)?

In the end it is my problem. I got the car tuned and the owner will not likely support further troubleshooting.

There seems to be something<> in the software that differentiates the two?

Thanks,

Bruce