VAG Ibiza III 2000 with engine ALM 1.6i 55kw. I can't pass MOT inspection because of rich mixture CO 10%, Lambda 0,7. Before changing fuel pump (which was bad) and with disconnected lambda MOT inspection showed CO 6%, Lambda 0,8. VCDS shows no engine faults. What can cause so rich?
cycle thru the ecu measuring blocks next, make sure all the sensor inputs are showing good values. maybe check the fuel injectors and fuel pressure regulator?
Problem was solved. O2 sensor was faulty and CTS showed value +10celsius. I have checked CTS wiring under hood according to manuals, even make additional ground and no luck, but when unconnected additional ground VCDS measuring block of coolant temperature sensor showed 66celsius. After MOT CTS failure came back again. Coolant temperature is not working at cluster. CTS resistance is OK.CTS is 4 pin. I will try to check measure block what is showing because engine has vibration... 42 pin of ECU resistance is OK under 1,5Ohm. ibiza2 by Vilius Juknevičius, on Flickr
I would say the 10 degree block is inlet temp rather than coolant temp? with ignition on unplug the combined inlet temp and map sensor and see if that block changes value. if you loop pins 1 and 2 on the coolant sensor your dash temp should go up, if it does then sensor is bad and if not suggests wiring is bad somewhere or cluster has packed in