Lambda value for VAGCOM

[SamG40 0]

Evening, can anyone please tell me what they see for the values on VAGCOM for a healthy lambda probe please? I've been getting a Lambda fault code and I had a failure on the MOT for emissions. It only cycles between 0.95 and 1.04 or so which to me dosent seem to be correct. I've done a search and cant really find a defintive answer.

 

The emissions failure was the CO2 level was 0.98 by the way with the limit being 0.30. Apparently it was fluctuating up and down.

[dr_mat 0]

The lambda cycling between 0.95 and 1.04 is about right actually. What's the fault code?

[SamG40 0]

I cant remember the exact error but it was something along the lines of the lambda value out of range and being intermittent. Surely the voltage should cycle to a lower voltage on idle. I was always led to believe that Lambda's read between 0 and 1 volts?!

[dr_mat 0]

Yes, but the VAGCOM value isn't volts, it's lambda.. The fact that the error is "intermittent" confirms to me that while you're reading it it's fine - 0.95-1.05 is right.

 

I guess you either have to replace it anyway, or keep reading the values until you see something that's genuinely bogus.

[SamG40 0]

Ah right, cheers for that. Well I replaced it last night. Will keep an eye on it.

 

If it isnt this that is causing my emissions though I'm a bit stumped. The car is running fine but the fuel consumption has been well down on what it used to be.

[dr_mat 0]

Look for air leaks, anywhere between the MAF and the lambda will cause mixture problems.

[SamG40 0]

Woohoo. Seems it must have been the Lambda. I've just got back from the MOT and it passed with a CO reading of 0 and a HC reading of 7ppm which now seems incredibly low!

[dr_mat 0]

Yup, sounds like it!

[Toad 0]

:)

 

Isn't the lambda set to show 1 at an air/fuel ratio of 14.7?

[dr_mat 0]

Yep, think so, 1 == stoichiometric a/f mix.