OBD2 Code P0129

[superjudge]

I read earlier this morning a thread that suggested a 99 New Beetle be checked at AutoZone when the 'Check Engine' light came on.

I took mine (same make, model and year) and it got OBD2 code P0129

 P0129 - C2 - Bank 1 HO2S 2 Slow Switching During Catalyst Monitor Test

Details on the code suggested that it is likely that the heated O2 sensor has failed, or to a lesser extent there's a fuel/air regulator issue.

I called the nearest dealership to ask what it would cost to repair and they said they couldn't go by the code, because they have their own computers for the job, and it would cost $55 to use it.

Is it likely that the testing tool at AutoZone is inaccurate (the tool is the size of a small paperback book, orange, and is on sale there) and they have a special tool for the job, or is it more likely that they just want to get us in there for $55 and do the same work and screw us on it all?

Thanks all for any help.

superjudge.

[boschmann]

The code that was set will be the same no matter which scanner reads it, the VW VAG scanner has much more capability to look at the actual engine data values, etc.... I do question the code # you say you got, are you sure that wasn't a P0139? I've never run across that P0129 & that has an interesting description. Either way it suggests either the rearward, post-cat, O2 sensor is not functioning optimally or that the catalytic converter is failing. The strange thing is there are separate codes for each of those (P0139 & P0420 or 422). I couldn't find the code in Bentley, I'll have to do a search on it. I'd clear the code & see if it comes back.

[superjudge]

Actually, they did it again and it came out P0172.

Fuel System Too Rich. The guy forgot it, and just agreed when I asked if it was P0129.

[boschmann]

That's a much more common code. Which engine do you have?

[superjudge]

2.0 Gasser.

[boschmann]

Well, official test proceedure goes through a long list of checks including engine oil dilution, intake & exhaust leaks, fuel injector problems.... Most commonly it falls back to a bad Mass Air Flow (MAF) sensor. You need a scanner that can look at certain data measuring blocks to properly diagnose, but since the part can be replaced yourself & it is fairly inexpenive these days (about $60) it's almost just as easy to go ahead & replace it.

[superjudge]

We checked the code on a site and it said "Fuel System Too Rich"

We put in some injector cleaner and it turned it off yesterday. We'll see what happens.