Mikaere808

My 2001 tt will not send communicate with the smog machine. Has anyone had his problem or know of a fix for it? I need to get it smogged so I can register it.

Thanks

Mister Bally

Get your hands on a wiring diagram (Bentley manual on CD) and trace the wiring from the diagnostic port to the main ECU as well as 12 volt & ground lines. Probably a break somewhere or a bad ECU communication circuit.

A good shop visit would probably be best but someone could have disconnected or cut something which is easy to diagnose using standard automotive electrical troubleshooting techniques.

Mikaere808

I was also told because the battery died that it reset the ECU. And that I need to drive it for awhile at 55mph or above to get the ECU working again. Is that true? Hopefully that's true cause that will be a much cheaper fix than taking it to a shop.

AudiMick

Nothing to do with the battery, you may need to drive it to get readiness codes but the scanner should still work.

Do you have an aftermarket radio?

There's a problem with some harnesses shorting the K-line to 12 volt. It will block communications.

The other common failures that block the K-line are the cluster, ABS module and comfort / alarm module. Unplug them one at a time to find the culprit.