VAG-COM Problem or User Error?!?!?!?

[rweir]

Guys,

I just go the USB VAG-COM yesterday. I had a wee 'play' with it in my car last night, all went fine (99 S4). I then tried it in my mates A4 99 1.8, on his I scanned for errors (brought a few up for alarm going off, took at note and cleared them). Then exited the system, I did close down VAG-COM and pulled the cable out.

This morning he called to tell me his battery was dead. Now that made sense since he left the internal light on!! He got a jump start. Then, his car would just cut out if he let the rev's drop, ie it would not keep a good idle speed so kept cutting out ...

He took it to a local garage who has a dealer VAG system, guess he told him what I had been using the night before and the garage said that it reported to him that the system had not been closed down properly and he had reset the ECU to it's 'defaults' ... ??

What went wrong? Or was it just the fact that every last bit of power was drained by leaving the light on??

Cheers,
Rich. [img]images/graemlins/s4anogaro.gif[/img]

[Carps]

Flat battery is my guess. You have to actually knowingly do something with VAG-COM to make changes - simply unplugging it won't cause any problems unless you are in the middle of some process (ie, throttle calibration)

[rweir]

I was hoping and thinking that myself, but my knowledge of this is not enough to be sure ...

Just feel bad that my mate now thinks I screwed his car up!
Any ideas how a flat batter could cause it loose settings then? Is the ECU hard codes, ie does not need a battery or capacitor to keep it going if the main batter is disconnected (or goes flat) ?

r

[Dippy]

In theory:

The problem with a battery going flat rather than just being disconnected is that the voltage slowly drops. There will be a critical point where the voltage is only just enough to keep the ECU active. As the voltage dips a bit lower, the ECU may not just switch off, instead it could get corrupted...

[rweir]

Thanks mate ... Just need to convince my mate that I am not the bad guy he thinks I am now!!

Anyway, last night next doors BM was nicked so think he has other things on his mind now!

r [img]images/graemlins/s4anogaro.gif[/img]