JCougar

So I started a thread about my car not starting yesterday. I tried to use VAG COM to check again if there were any fault codes besides my oxygen sensor, but now the only control module it will read is the HVAC module (08). I did the auto scan, and I also tried specifically reading the fault codes from the Engine module (01), but it simply does not connect to the engine module (or any other module besides the HVAC).

This seems peculiar to me. How can it connect to one module but not any others? Does this mean my ECU is fried or something? My car doesn't start, and I thought it was the fuel pump or the ECT sensor, but now I'm concerned that the ECU itself is messed up. My battery is lower than normal from all the cranking I did in the last two days, but it is not dead. It will still crank. Could a lower voltage be messing with my ECU?

I'm thinking I'm just going to have to give in and get this car towed to the mechanic.

4Driver4

You need proper voltage to run the control units. Make sure the battery is fully charged. Stop running the full scan if you don't need to; look at each control unit separately. Autoscan is a colossal waste of time.

AudiMick

Agree, some modules won't run with low voltage.

Also unplug your ABS module, those things seem to quite often prevent a scan if they are flaky.

hdnorm

i am an audi tech so maybe i can help, first off the hvac is not on the CAN bus so this is probably why you can read the ECM.is there an after market radio installed? if so make sure the data bus wire is disconnected or you wont read the modules.now first charge the battery,check all fuses then check to see if your check engine lite comes on when you turn on the key,if not you have either a faulty ecm or cluster.did you jump start the car an accidently revers polarity? when you open the door and turn the key on you should hear the fuel pump prime.if all these are good i suspect one of the modules on the can bus is taking all down. the first module to usually cause this is the airbag module then the abs.any more questions you can email me at hdmacguyver66@yahoo.com

AudiMick

Not to be picky but: There is no CAN-bus on a B5 A4.