RocketyMan

Hello, I've been lurking the forums for quite some time and decided to sign up and ask for help as I am literally out of ideas.

I have a 1998 Audi A6 C5, AHA 2.8L Quattro. I get check engine codes for the MAF as well as both bank 0 and 1 being too rich. In addition, the vehicle has sluggish shifting (most likely due to the ECU not being able to calculate the correct load from the TPS and MAF sending bad signals).

I've looked in the Bentley service manual and found the G70 connected to pins 12 and 13 directly. Pin 13 has this "shield" wire as well. One thing I don't get is how the G70 isn't actually connected to pin 10 on the ECU. I looked at the plenum connector and there is no female pin on pin 6 of the beige (brown) connector, contrary to what the service manual says.

I've been trying to follow this post: https://www.audiworld.com/forums/a4-...-trace-350765/
I know its on a B5, but it also has the 3 pin MAF, AHA motor. I can't seem to find anything wrong with my grounds.

Any advice? Please help.

P.S. I replaced the MAF with an authentic new HITACHI brand.

RocketyMan

Attached you should see the beige (brown) connector. There's no pin 6 in the female beige connector. All this pin does is give S231 fused 12v power.

RocketyMan

As an update for everyone, I have the DTC codes.

Confirmed: P1129 -- Long term fuel trim, entire speed/load range, bank 2 too rich

Pending: P1141 -- Load Calculation cross check, P1127 -- Long term fuel trim, bank 1 too rich

I did replace the fuel pressure regulator a while back as well. And even before that I cleaned the fuel injectors manually each individually a long time ago. Tried searching the forum some more and only came up with stuff I've already tried. The last thing I can replace are the O2 sensors...but both? I'm not sure the O2s are exactly to blame.

Still need help.

Harleyguy

Sounds like bad O2 sensors to me. Having said that it could be a faulty wiring issue as well, still related to the O2's.

RocketyMan

Both banks of O2 sensors being bad? I suppose it's possible.

I use to have a VAGCOM but not anymore. Now all I have is just a regular scanner. How would I test to see if the O2 sensors are good? Just see that they're switching voltage from .2 to .8?

Harleyguy

Looking at the photo, it appears that pin 6 is broken off on the female plug but the male side is wired?? Try using a mirror and determine if there is a wire on the female plug where the pin is missing. If so that could be the problem also. Also a VAGCOM scan would probably help a lot. Maybe a friend or trusted indy shop could help with that.

georgeb944

The wiring diagram for the 1998 AHA A6 looks different from the one you are showing.

I would look at the O2 sensors (all of them).

RocketyMan

I took apart the brown connector at the plenum and saw that there was actually no wire present at all. Seems kinda weird. From what I gathered from searching some other posts, the ECM just takes the ground and signal wire, pin 12 and 13 respectively from the MAF. The power is just derived from S231 (fuse 31).

Yes, I don't have the full version for the AHA A6. So I've been adapting off the "ACK,ALG/AGA,AJG,ALF,ALW" Bentley manual, unfortunately.

Now when you say look at all O2 sensors, are you suggesting they would be needing replacement? I thought rich conditions produce high voltage on O2, and a lazy O2 would switch lower and lower voltage. But an O2 sensor can fail "high" with always giving off high voltage readings??

I checked the connectors on the fire wall, but what else would you do to suggest checking them? I could take them out and try and clean them with a low VOC solution, ya?

georgeb944

Actually, the best way to check them is with the VagCom or VCDS. Other methods might not catch a lazy or non functioning O2 sensor.

RocketyMan

Yeah..I wish I still had my VAGCOM...but not anymore :/

I have a scanner I can graph the O2 readings.