View Full Version : 30v 2.8 o2 sensor threshold values (trblshooting cat ineffcy)

01-09-2008, 10:11 PM
i've been trying to fix this CEL for over a year now, P0430 cat ineffeciency. getting it on bank 1 and 2 and i can smell the exhaust when i'm at a stand still sometimes, so i'm sure the cats are shot. i got a CEL for a misfire on cyl 4 so i decided to replace the plugs with some bosch plat 4+'s. now that i know that's no longer the problem, here's where i'm at.

2001 a4 2.8 quattro tip w/ 127k miles.

i have vagcom, is there a way i can look at the o2 sensor values to make sure they're reading/responding correctly? i don't want to replace them if i don't have to of course. i have 2 aftermarket cats to put on but i want to make sure something doesn't foul them up again if the spark plugs weren't the issue. if it's not the o2 sensors, i can't imagine what else it would be. i've only always gotten cat codes, nothing that in all the research i've done says o2 sensors.

and the readiness test is one way i've heard also to check if they're fine but i'm not sure exactly what to do w/ the numbers it gives you, anyone care to be a little more specific w/ that?

01-10-2008, 08:40 AM
fyi, got this response from audiworld. seems helpful.


G130= O2S behind three way cat converter, bank 1
G131= O2S behind three way cat converter, bank 2
Use the VAG-Com to read measuring value block, display group 041.
If you use a multimeter to check it at the sensor itself, then check for continuity between the GND wire and signal wire(terminals 3 and 4). If there is continuity, replace the sensor. At room temps, the values between terminals 1 and 2 should be approx 2 to 5 ohms.

Comments: It would not surprise me that at that mileage the sensors are getting somewhat tired. It also depends alot on the maintenance history of the car. On the ATQ engine, you might consider sticking with the standard NGK coppers, I find they have some of the best detination quality for those engines(ie less misfires or fouling). You might also consider changing out the coolant temp sensor, which can greatly effect the fuel mixture and idle. Audi came out with an updated version awhile back. If you have not done a fuel filter in the last 30k, you might consider doing so. It can greatly effect rest and running fuel pressures. This can make a weakened or diminished spray pattern, one that is not totally atmomizing the fuel effectively. It results in misfires, unburnt fuel going into the cats , or washing down the cyls. Having some sort of reliable basis to work off from is critical.