aaronazevedo

Hello everyone - I realize that this is the D2 A8 forum, but I have a C5 A6 with a 4.2 motor and a 6-speed swap. We share much of the drive train and I haven't had any luck on the C5 forum.

I've owned our C5 A6 4.2 for about 5 years and put about 50k miles on it. Relatively trouble free outside of regular maintenance items, and standard 'old car' stuff.

The auto magic transmission was starting to shift hard into 2nd or 3rd. I had done a fluid and filter swap at 100k when I bought it, but figured I could check of a 'bucket list item' as well as get another 50k out of the car if I put a 6 speed in it. So 4 months ago, we drove down to Tucson and had a 6 speed swap done on the old girl. Wow! These cars should have come with a 6 speed from the factory. I was and still remain stunned at the torque and power of the 4.2 and frankly never realized it before when the slush-box was in the car. Fun times.

Well mostly fun. From the moment I picked the car up, I have had the ECS and ABS light come on at random times for 3-5 seconds. The car 'dials back' power for that brief time, and then is all back ready to go. Your first question should be 'why didn't you take it back the guy?". Well, good question. the real answer is, I was a on a fixed 10 day schedule and needed to get back on the road headed north. Work meetings called and I had no choice; other than leaving the car there and fly home. We drove, with the idea that I could just swap out the MAF and be good as new. Not so fast. It didn't work.

For 4 months I've been dealing with the following codes:
17521 - Oxygen (Lamda) Sensor, B1 S1, P1113 - 35-10 - Internal Resistance too high - Intermittent
16486 - Mass Air Flow Sensor (G70) - P0102 - 35-10 - Signal too low - Intermittent
18265 - Load Signal - P1857 - 35-10 - Error Message from ECU - Intermittent

Like I said, I have replace the MAF with a new Bosch unit. . I don't think I have an ABS issue, but I could be wrong given that the ABS module now gets 'different' directions from the ECU now that it is coded to an EU manual transmission car.

The guy who did the swap has been supportive in working through potential issues with me. Current thought is the ABS module. The EU code has been used successfully on dozens of cars. and 90 % of the time, my car runs fine, so I don't think that the tune is wrong or at fault.

Could a faulty O2 sensor give this issue? the O2 has been bad for years, and I frankly don't care about emissions. Neither does my State.

Any thoughts? Any experience here?

I thought I might have broken wires between the MAF and the ECU, but today we tested them and they all have great continuity.

I'm now wondering about a failing ABS module?

Any thoughts or experiences to share?
Greatly appreciated - Aaro