No signal on Lamda probe but apparently a wiring fault......

[Nick_Micouris 0]

failed my MOT on emissions at the weekend and I went to VW to get a diagnostic check done with the VAG computer VAS 5052 and the readout gave the following:

 

Vehicle System

01 Engine electronics

021906258AG

MOTOR

Coding 1

 

----------

 

02 Interrogate fault memory:

3 Fault/notes detected

 

 

00525 003

Lambda Probe -G39

No signal

 

00561 014

Mixture adaption

Adaptation limit (add.) exceeded

 

00561 014

Mixture adaption

Adaptation limit (add.) exceeded

 

 

 

He was adamant that the Lambda probe was not faulty and that the wiring between the Lambda and the ECU was at fault and I gave him £50 cash to sort it as a private job. Took him about an hour to sort.

 

Off to get my MOT retest and I sure hope that it was a wiring issue. He didnt make it clear which wires were faulty but wanted me to understand that I had been given a real bargain! In truth, if the wires really were faulty in the engine bay, then I suppose £50 is great.

 

Has anyone else had a similar thing? I would have thought that the lambda probe was dead, myself but it seems not.

 

If the lambda probe was dead would it have given it a different reading to "no signal"?

[Kevin Bacon 5]

The best way to check lambdas if you haven't got VAG-COM is to stick a high impedance meter across the signal wire (white) and chassis earth. If the voltage fluctuates rapidly (after the 2 minute preheat period when cold) then it's fine. If it's stuck at 0.45 V it's dead in which case I don't think OBD1 codes it, it will just give you the adaptation errors as the ECU will run out of fuel trimming options.

 

The most common cause if wire breakage is when exhaust fitters twist the probe wires around on themselves when removing and refitting it but I'm not sure if that's relevant in your case.

 

£50 is a bargain as wiring fault finding is time consuming and tedious!

[Nick_Micouris 0]

well, we did replace the front pipe last year, so you never know.... it could have been me...

 

Whatever happens, I suppose the proof of the repair will be in the MOT retest!

 

What I did find stranfe is that he said - "before you go for your MOT, make sure the car is warmed up". Not sure why he needed to tell me that as I didnt think they would test it until it was warm anyway!!

[Kevin Bacon 5]

They don't generally. All petrol cars run rich when cold so they do the CO test when hot. They do the mechanical checks on the ramp whilst the engine is warming up first....

[Nick_Micouris 0]

seems it was a wiring fault for sure!

 

On the retest, my co2 reading was 0.1% - superb!! :)