P0040

P0040

Oxygen sensor ahead of catalytic converter - signal implausible (only Turbo)

Diagnosis conditions
- Battery positive voltage between 10 V and 16 V
- Time elapsed after engine start-up greater than 10 seconds
- Oxygen sensing system active

Possible fault cause
- Oxygen sensors ahead of catalytic converter exchanged
- Line polarity reversal in wiring harness
- Simultaneous occurance of leaking fuel injector on the one bank and leaking intake distributor on the other bank

Affected terminals
DME control module connector II, pins 2, 5, 6, 9, 10, 15, 16, 24 and oxygen sensor jacks ahead of catalytic converter, pins 1, 2, 5 and 6

Diagnosis/troubleshooting

NOTE:
- Diagnosis detects oxygen sensor - regulators running contrary to the adaptation limitation.
- For example: The regulator for bank 1 detects an excessively rich mixture and wants to make it leaner. At the same time, the regulator on bank 2 detects an excessively lean mixture and wants to make it richer. If the oxygen sensors or their signal wires have been exchanged, the detected bank 1 continues to make the mixture richer and bank 2 continues to make the mixture leaner. Only when both oxygen sensors remain on the opposing stops for a certain period of time will this fault be recorded.
- Do not use contact spray on the oxygen sensor plug connections as this may cause irreparable damage to the wiring (contamination of the oxygen sensor via the reference air channel).

Part 1:

Part 2: