Need help with Fault codes please


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Aug 8, 2007
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I just got my vag-com and ran it for the first time today.
(Check engine light has been on and I didn't want to go to the stealership).
Got a couple of codes I can't find anywhere.
Obviously, I have a bad oxygen sensor.
Question is - apparently there is a heated oxygen sensor before the cat, and another sensor behind the cat, which sensor is bad?
It looks like I've got a code from both sensors, could one sensor going bad have caused both to produce fault codes?
If anyone has any info on these, I'd sure appreciate it.

17522 - Oxygen (Lamda) Sensor; B1 s2: Internal Resistance too high
P1114 - 008 - Implausable Signal - MIL ON
17524 - Oxygen (Lamda) Sensor Heating: B1 s2: Open Circuit
P1116 - 004 - No Signal/Communication - MIL ON
They both look to be the same unit, a lamda sensor has both a heater and an oxygen sensor in one unit

So i'd say that its the first sensor the lambda sensor, maybe its disconnected ? likely that it is faulty

The lamda detects the corect air fule ratio for the ecu so will not be helping mpg or engine if its not working properly ! I don't belive they are too expensive ?
That kind of fault description is fairly common to a knackered one. Things like Open Circuit, High Resistance, Short to Ground/Plus.... All signs of it not functioning properly. Its the one before the CAT I reckon.
As Longman says, you have a knackered sensor. In fact, it is most likely the heater element in the sensor that has failed. The sensor will not heat to the proper temperature, the sensor output will be out of spec, and the ECU will run open loop, producing more emissions than the engine is supposed to produce - hence the MIL indicator being on.

To help identify which sensor, try this diagram:

I'm not certain your car is exactly as this diagram but I think VAG cars use the same scheme - I think - I am not sure of this.
Handy diagram that Bruce. Even if a 1.8T only has the single CAT setup, That diagram will show the which one is pre and which one is post CAT.

ie Post CAT has gone on the one above... Does that sound right?

I guess a single CAT exhaust system would just not have the B2 sensors?
That is my understanding - but then, I'm not the tech expert here. My role is business operations and like most in these forums, I am always learning. This question has come up before about the sensors and the "boss" sent me the diagram so I could help those calling in to Ross-Tech. So, yes, I think the identifiers are consistent. You only have one bank but you still have a pre-cat and post cat sensor. The best place to get the answer is the official repair manual.
I do have the Bently manual on CD, but I was unable to identify which sensor with the manual. It's more difficult to navigate the CD than the real manual. I'll be buying them in print from now on.
That being said, the first couple of responses suggested the sensor before the cat, however both codes have b1 s2 in them, so based on the diagram from Bruce@Ross-tech, I gather it is actually the one behind the cat, s2?
If anyone can verify or at least agree on the interpetation, I'd feel better about dropping the $140 on a new sensor. I'd hate to replace the wrong one....
I'll ask at the office tomorrow to confirm but I am pretty confident that S2 is behind the CAT.
After looking at the diagram, I would day that its the Post CAT sensor you need. Got it wrong first time!
I checked with an expert in the office and he agrees: S2 is the after CAT sensor as the diagram shows it.