hi all

My 99 octy estate has failed its MOT on emissions,and I was told by the mechanic that it was the Lambda sensor.he couldnt say which one it was and I cant afford to change both this close to christmas.the CO readings were fine,as were the HC readings.Its the lambda readingsthat are high.should be 0.970-1.030 and mine were upto 1.367.Ive had it checked by VAGCOM and on bank 1 the lambda reading looked OK ,but on bank 6 the reading was stuck at 25%.Can anyone tell me if it is just one that has gone ,and also where are they plugged into.I can see the one on the manifold but lose the wires as they enter the bulkhead.Any help and advice would be greatly appreciated.

sorry should have added its a 2.0 petrol AQC engine

Edited 13 December, 200817 yr by zoobie

if it's failing emmissions it won't be anything to do with the rearmost sensor, that one has no control function as such, just monitoring of CAT operation, and as such would be expected to be sat at a static value if the CAT is working correctly.

if CO and HC values are OK then I'd be looking for air leaks in the exhaust first, allowing air to get into the exhaust stream and messing with the LAmbda value

Normally if the lambda sensor has a problem it will push the CO and/or HC values out