Possible causes
– HO2S Bank 1 and 2 Sensor 1 harness is open or shorted
– HO2S Bank 1 and 2 Sensor 1 circuit connectors (wrong connection)
– Faulty Engine Control Module (ECM)
– HO2S Bank 1 and 2 Sensor 1 circuit connectors (wrong connection)
– Faulty Engine Control Module (ECM)
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P0040 AUDI OBD Code Description
The heated oxygen sensor (HO2S) monitor determines if the HO2S signal response for a fuel shift corresponds to the correct engine bank.