nyrobbie77

About once or twice a month, my MIL light comes on. Typically its for a lazy rear 02 sensor, code P0137, but once every 3rd time the light comes on it will also have code P0103 for mass air flow. On the list is to replace both rear 02 sensors, just haven't gotten to it yet. The P0103 first came on a few weeks after installing a new K&N filter, am guessing some oil got on it and just needs to be cleaned.

Back in November, about a mile after starting up engine cold, outside temps low 30s i think, I noticed all the PRNDL lights were lit up on the dash board. Car drove just fine, no limp mode, no banging shifts etc. I shut the car off and restarted it and didn't come back on.

Now yesterday morning, just after the MIL light came on I noticed the PRNDL lights all lit up again. Restarted the car and the PRNDL lights were normal. Went to drive home, and PRNDL lights were on again after a mile of driving. Restarted the car and PRNDL lights stayed off for a couple miles and returned. MIL light was on this whole time, again car drove and shifted fine. When I got home (trip to work is about 35 miles each way), I read the MIL codes with a reader before shutting the car off, only had the same P0137 and P0103. When i cleared the codes the PRNDL lights turned off too. My drive into work this morning and no lights came on at all.

I'm wondering if the PRNDL issue might only be found with the VAG-com tool (i had only scanned with a basic reader)? Also, i've read that oil intrusion into the shift harness may cause some fault codes and the PRNDL lights coming on. I know i've got a good oil leak down both sides of the engine, so this may be the culprit. What do you all think?

btw, car is 97 A8 quattro with 170k miles.

thanks in advance

tozoM8

You need to replace your MAF.

nyrobbie77

I'm going to try to clean it first. i only get a MAF code once every month or two. I drive over 400 miles a week. if it was truly shot, i would think that i would get a fault code much more often.

This morning on the way to work, after about 35 mins of driving the PRNDL board light up again, no check engine lights. hopefully? it comes on again tonight and i can scan with the vagcom tool.

tozoM8

You can scan it before the CEL. You already have the code there.

nyrobbie77

I just wanted to update this thread for the archives. I cleaned my MAF sensor a few months back, it had greasy goop on it presumably from the k&n filter I had put in. it was a brand new filter, they must've over oiled it in the factory.

since then I have had no more active or pending codes for the MAF and the PRNDL lights haven't all lit up either. I've driven several thousand miles and still no codes, active or pending. I read somewhere that someone else had a similar issue, that the loss of signal from the MAF made all their PRNDL lights come on. i'm not sure why or what the logic is behind that, but am glad that its fixed.

I still have to replace that O2 sensor. the engine light is on constantly for it and my safety/emissions inspection is 4 months over due haha. the base of the O2 sensor is fairly rounded off, even with the crow-foot O2 sensor tool I can't get it out. I think i'll have to end up removing the catalytic converter and try working on it that way. worst case I will take it to a exhaust shop once I get the CAT out.