Tranny Slip and Check Engine Light On After Battery Disconnect


Asked by JonJ1998 Dec 28, 2009 at 03:40 PM about the 1998 Audi A4 1.8T Quattro

Question type: Maintenance & Repair


Please help! I just bought a 1998 Audi A4 Quatro with the 1.8T. I drove the car for about 3 days and everything was great! The car did not come with a radio as the previous owner had an aftermarket and he removed it prior to selling the car to me. Yesterday, I drove the car and went out and bought a radio. I drive back to my house and everything's great. I remove the negative battery cable, install the new radio, reconnect the battery cable, and the check engine light is on. I try to drive around the block and the tranny is slipping into every gear. The car has no tranny leaks or any other leaks for that matter. Is there any way I disconnested a wire behind the radio or something? Seems extremely strange that the car was great until I installed a radio, and now engine light is on and tranny slips. Please please please help! This was a Christmas gift and now the car in not driveable.

Thanks in advance.


2 Answers

Patrick Pasterski

Anytime you disconnect the battery the ECU needs to "relearn" engine idle parameters, shift points etc. Also the ECU could have been flashed at a dealer with newer updated parameters which will have been lost when you disconnected the battery. Disconnect the battery again and let it sit for a few minutes. Reconnect the battery and start the car but do not touch the gas peddle or put it in gear. Let it idle, with all accessories turned off for about 2-3 minutes. Drive it until it's at normal operating temp(dont drive it hard) and let it idle for another 5 minutes. Turn it off and let it sit for 30 minutes.

2 out of 2 people think this is helpful.

I bought a 2001 Audi A4 1.8T, Avant on Saturday and everything was working fine. It drove perfectly. I than replaced some globes and fuses cause some lights did not work. In the process I left the lights on. I than fixed a jammed seatbelt. When I wanted to start the car, it did not want to start as the battery was too flat. I disconnected the batter and charged it. After a while I tried again, but with no luck. I tried different stuff in an attempt to start it again including disconnecting the ECU for an hour or so. Even up to today it does not start. The car never worked with the remote, although I have one, only with the keys. The guy from whom I bought the car had the keys made recently and it hasn't been coded. My concerns are: (1) does the seatbelt have an effect? (2) does the key need to recoded or what? Can somebody help me please?

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