code P1128 from CE light on 2001 Jetta GLS

[zackforbing]

this is the second time it's given me this code...the first time, I had autozone cancel it out, thinking it was just a loose fuel cap, but the light came on again after a few days, reading the same code, a P-1128 (air/fuel metering) ...has anyone had experience with this, or know what to do about it? I figured I'd check here first before taking it in since I am a poor college student and I don't have time to take it in for a few days anyway.

thanks for any help!

[boschmann]

I don't know which engine you have, but the problem is probably the same regardless. The code is set because the the oxygen sensor is reporting the mixture is so rich that it is on lean limit. There probably isn't really a problem with the engine running too rich, just that the O2 sensor thinks it is. It's very common for these O2 sensors to go bad, but it might be worthwhile to let someone with a scan tool view the actual datastream to see that the sensor is not reacting.

[zackforbing]

sorry, I've got a 2.slow...and I need to check to see how many valves I've got..I can't remember. but thanks for your help!

[boschmann]

By the way it's the forward or pre-catlytic converter O2 sensor that goes bad most oftem.

[zackforbing]

it's probably worth noting that after i filled my tank, it went out for a day...and then came back on. so you guys think I should take it to the dealer? I don't really have any money to throw around, so I only want to take it in if it's serious.

[boschmann]

Our local dealer is selling them for < $20 because there has been so much trouble with them, so I would get it there. They're fairly easy to put in so most any shop can do that.

[Kirkit]

I had the same reading, P1128, The dealer I bought the car from had the O2 censors changed, it didnt fix it. What fixed the problem on my jetta was what I seen Bosch post in another, The Mass Air Flow Censor. Which has an extended warranty due to faulty censors.

[danray11]

I have had a similar code.. first try sparying the throttle body out.. then use electrical cleaner and clean the M.A.F

[kump]

My wife's car has had this off and on for about a year. I repalced a rotted vacuum hose, turned it off and it stayed off until she hit the interstate. Being a former master auto tech I tried everything I could think of. Cleaned throttle body, checked all sensor connections, replace air filter, tightened fuel cap, all to no avail. Upon changing the oil, the dipstick tube (VW calls it a "funnel") crumbled when I pulled the dipstick out with the engine cover removed. Thinking that had to be it, I replaced it and used a friend's scanner to reset the light. It stayed off until she hit the highway again. I guess I'll look at the datastream from the 02 sensor next. Life would be so much easier if I owned a scan tool for ODBII!

[TmanJetta2.0]

In my experience it's the MAF... Same issue here, and I fixed it in about 10 minutes. Schucks sells a remanufactured MAF sensor for about $85 after core. It will take about 2 minutes to remove your MAF, and about 2.5 to reinstall. Seriously. I had the 1128 on a 2000 Jetta 2.0 GL and I knew it was the MAF thanks to forums. But after trying to clean it, the CEL came back on. Paid $91 diagnosis at the shop, and they wanted $300 more to fix. That's $200 for the part, and another $100 to install. I got mine at Schucks, installed in the parking lot, used their complimentary code reader to reset the CEL, and it's good to go. MAF!