Vag-com not communicating with ECU or TCU

[MantanaB6]

I'm posting this in the B6 A4 forum cuz I'm hoping for a quick reply. I have a B6 S4, and it is currently with my mechanic getting some things done, and I asked him to scan my car as a CEL just popped up the other day. I assumed it was from a failing SAI pump (heard the dreaded whirring sound the other morning). Anyways, he plugged it in and said it is not communicated the ECU or TCU. It is communicating with the central convenience however. I drove the car to the shop this morning and both the engine and transmission seemed to be behaving normally. What could cause this? I'm trying to help him diagnose this so he can focus on fixing the other shit on my car and I can still pick it up at the end of the day.

[Hugh@EuropaParts]

Silly question but is the key in the ignition?

[blitz2190]

I'm posting this in the B6 A4 forum cuz I'm hoping for a quick reply. I have a B6 S4, and it is currently with my mechanic getting some things done, and I asked him to scan my car as a CEL just popped up the other day. I assumed it was from a failing SAI pump (heard the dreaded whirring sound the other morning). Anyways, he plugged it in and said it is not communicated the ECU or TCU. It is communicating with the central convenience however. I drove the car to the shop this morning and both the engine and transmission seemed to be behaving normally. What could cause this? I'm trying to help him diagnose this so he can focus on fixing the other shit on my car and I can still pick it up at the end of the day.

does it have an aftermarket radio, I know weird question but some have been shown to affect the can gateway.

[MantanaB6]

It has a 2012 RNSE, however I scanned it 2 weeks ago and didn't have any issues (pre-CEL). I assume the mechanic has the key in the ignition (he's a friend and probably the best Audi tech I've ever dealt with).

[blitz2190]

It has a 2012 RNSE, however I scanned it 2 weeks ago and didn't have any issues (pre-CEL). I assume the mechanic has the key in the ignition (he's a friend and probably the best Audi tech I've ever dealt with).

that radio shouldn't effect it, make sure the is in the on position. Can't tell you how many times I've forgot that one. Short of that it may be a failed module on the drivetrain canbus. One module will wreck communications on the whole bus if it has a short on the canbus wires.

[MantanaB6]

that radio shouldn't effect it, make sure the is in the on position. Can't tell you how many times I've forgot that one. Short of that it may be a failed module on the drivetrain canbus. One module will wreck communications on the whole bus if it has a short on the canbus wires.

Hmmm, how would you go about determining that?


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[blitz2190]

if the key on doesnt solve it, the simplest way would be unplug each module until you have communication. If that doesn't work it could be either the wires(you'll have to check by hand or a multi meter), or less likely the can gateway.

[MantanaB6]

if the key on doesnt solve it, the simplest way would be unplug each module until you have communication. If that doesn't work it could be either the wires(you'll have to check by hand or a multi meter), or less likely the can gateway.

Turns out the brand new Ross-tech cable wasn't working. Used and old cable and worked. Freak out for nothing!


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[rocket1420]

Turns out the brand new Ross-tech cable wasn't working. Used and old cable and worked. Freak out for nothing!


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Geeze man, sometimes the simplest solution. Most of use would've been chasing wires for hours.

[MantanaB6]

Geeze man, sometimes the simplest solution. Most of use would've been chasing wires for hours.

Seriously. So note to people that get new Ross-Tech cables and run into this issue, try an old Vag-Com cable before tearing your dash apart.


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