ECU problem


Registered User
Jan 2, 2014
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Hi I wonder if anyone can Help? Im having a problem with my A4 B6 about a week ago my car broke down and the AA man said it was the ECU as fuse 29 (engine management) kept blowing ,so checked on various forums at symptom's( fan staying on, head lights not working)so I took the old one out and ordered a ECU from ebay and was going to get it reprogrammed. I then read a thread about water in the ecu casing so went and checked mine as it was dark when I removed the ecu and there was about 2cm of water in the bottom of the box (im not sure if the water got into the ecu casing before or after I had disconnected the battery & removed ecu . I removed the relays (219,369,373) and they were full of water. I pulled the relays apart and left them on a radiator to dry as they had no visible signs of damage and dred out the casing (but ordered new relays). when the ebay ecu arrived and battery had been recharged I thought I would out of curiosity just try the old ecu and old dried out relays and replaced fuse 29 to see if it would work when the I connected the battery and the fuse didn't blow I was quite surprised and chuffed but once I tried to turn it over I seen smoke coming from 1 of the coils so I disconnected the battery. when the new relays arrived I put them in and noticed that had mixed up relay 219 and 369 and put them in the wrong way round. I replaced the relays with the new ones but now the will not turn over at all.

Any suggestions would be greatly appreciated
Good luck mate,ive no idea? Someone mgt give advice in a bit,just got to hang it out...
That could be an interesting fault to try and resolve. I presume you have checked all the fuses in the various fuse boxes, when smoke is coming from somewhere there is a lot of current flowing which can burn out wiring if it's not designed to carry that kind of current.
What year /model is the car you don't say whether it's diesel / petrol.

Dint plug the ecu in untill the fault is fixed. I cam clone your old ecu onto the new one or come and program them if your local.
Hi Karl,Thanks for the response, the car is a 2003 A4 3.0 automatic petrol, I have checked all the fuses and they are fine also got the fault codes

16891 - Idle Control System RPM Higher than Expected 16815 - Warm Up Catalyst; Bank 2: Efficiency Below Threshold 16539 P0155 O2 Sensor Heater Circ.,Bank2-Sensor1 Malfunction 17072 - ECM Power Relay Load Circuit 18068 - Coolant Fan Control 1: Short to Ground 18010/P1602/005634 - Power Supply B+ Terminal 30: Voltage too Low 17069 - ECM Power Relay Control Circuit
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I havnt put the new ecu on just tried putting the old one back on, im in Weymouth Dorset