02 a4 b6 no start no crank!

[Jamesy]

02 a4 b6 had water in ecu compartment. Aux fan was coming on. Replaced relay to fix. Was running super rough. I changed plugs and wires after it wouldn't start anymore. Tried starting it and cranked and cranked, it wouldn't start and then something "popped" and a little smoke came drifting up from around ecu compartment. Now it won't crank at all. Any ideas????? I need my car back! Only 150,000

[KHARDa4]

Ouch smoke from the ECM is never good. Probably fried it. I would try communicating with it via vag com or some scan tool. Check your fuses as well but by the sounds of it you may need a new ecm, sorry! Good luck!

[hightime80]

Yep your ecu is screwed. Try hooking up vcds see if it will communicate. If it does then use vag eeprom programmer to retrieve the skc then you can readapt another 02 ecu to it.
If it's a bit over your head try pm "k0mpressed" here on AZ. He runs his own tuning business and he is a whiz and he can probably hook u up with an immo defeated ecu in the worst case scenario.

[Jamesy]

Thanks guys. Would an ecu/ecm from an 03 work in my 02 after programmed?

[Let it snow]

Check your fuses in the ECU box and kick panel. You might get lucky.

[Jamesy]

I did. No luck. I also replaced all relays.

[KHARDa4]

Thanks guys. Would an ecu/ecm from an 03 work in my 02 after programmed?

No I don't believe so. 03-05 are compatible with each other for some reason the 02 is different.

[Let it snow]

Does the engine not turn over at all now? That may be a problem with your starter relay circuit.

[Jamesy]

Ok. Junkyard has an ecu for $100. The shop I brought it to replaced the starter thinking it was that. It didn't help. The car won't try and crank/turn over at all. It was trying to start before that "pop" and slight smoke coming from ecu compartment.

[Let it snow]

J434 is your starter relay. Under the ECU it is the last one to the right. Remove the relay. With clutch pedal pushed in or transmission in park check for voltage at pins 1 and 2 when starting. You should have 12 volts.

[diagnosticator]

No I don't believe so. 03-05 are compatible with each other for some reason the 02 is different.

An immo adapted (or immo off,) '03 ECU will work in a '02. The problem with the '02 is the ECU is different internally, and won't accept '03> software, but is pin for pin compatible otherwise. IE, since the ECU harness connectors are pinned the same, the same input and output signals are used with both the '02 and '03> ECUs.

The '02 and '03> ECU wiring diagrams are the same. If the '02 ECU wiring diagrams where different than the '03>, the ECUs would be incompatible.

[Jamesy]

Thanks guys. I will try that. The junkyard gave me an ecu from an a6. I was like "you sure this will work?" He said it would. Said the numbers matched up and it would be compatible besides the programming.

[Jamesy]

Thanks guys. I will try that. The junkyard gave me an ecu from an a6. I was like "you sure this will work?" He said it would. Said the numbers matched up and it would be compatible besides the programming.

An 02 a6

[Let it snow]

The engine not cranking/turning has nothing to do with the ECU. Start diagnosing the starter circuit then move on to possible ECU problems.

[diagnosticator]

The '02 A6 ECU will NOT work. The A6 is a V6 your car is a 4 cylinder, (right?) the harness connector for a V6 is NOT pin for pin compatible with the harness connector wiring used with a 4 cylinder engine.

What "programming" are you referring to in your post? A 1.8T ECU from a '03> A4 B6 does not need any programming other than matching the immobilizer to your immo ID in the instrument cluster. ( or setting the immo OFF in the ECU,) The ECU coding value needs to be entered with the same coding value as the original ECU also.

[Jamesy]

Hi guys. Just wanted to update. I'm having the car towed to Audi. Hopefully they can diagnose the problem. Thanks for all your help.

[maurizio]

you went to dealer?
bring some of this:

[Jamesy]

Well Audi just called me. Says it needs $2300 worth of wiring and new relays before they can diagnose.

[customa4]

Well Audi just called me. Says it needs $2300 worth of wiring and new relays before they can diagnose.

$2,300 before they can diagnose?!?!?!?

[Jamesy]

Ya. I'm just gonna get it towed home and try again.

[A4SoftWalker]

Yep your ecu is screwed. Try hooking up vcds see if it will communicate. If it does then use vag eeprom programmer to retrieve the skc then you can readapt another 02 ecu to it.
If it's a bit over your head try pm "k0mpressed" here on AZ. He runs his own tuning business and he is a whiz and he can probably hook u up with an immo defeated ecu in the worst case scenario.

Just chiming in with Troubleshooting tips I dont post much on here any more:

1) You had water in your ECM.
2) You had a "pop" occur when attempting to start car with associated smoke coming out of ECM.
3) Car no longer cranks.

Easy Solution:
1) Find and fix source of water leak.
2) Replace ECM with known compatible immo defeat unit from k0mpressed (or whomever)
3) Replace associated relays.
4)Check all fuses.
5) Start and drive car.

Thorough Solution:
1) Find and fix source of water leak.
2) Test ALL associated fuses, relays, and ECM - find whats bad . Dont forget the fusible link on the engine block.
3) Replace anything found not working in #2 above.
4) Replace ECM with immo-coded version to match your key fob if its bad.
5) Start and drive car.

All this towing... and starter swapping... and junkyard ECM swapping (without immo defeat) is absolutely time wasting and self-frustrating.

Keep it simple and focus on the problems that caused your issue.
Gud Luk.