P0040
P0040Oxygen sensors in front of catalytic converter exchanged - signal implausible
Diagnostic conditions
- Battery positive voltage between 10 V and 16 V
- Oxygen sensing system active
Possible cause of fault
- Oxygen sensors ahead of catalytic converter exchanged
- Line polarity reversal
Affected pins
DME control module, connector A, pin 4, and oxygen sensor ahead of catalytic converter, bank 2, pin 4
DME control module, connector A, pin 5, and oxygen sensor ahead of catalytic converter, bank 1 pin 4
DME control module, connector A, pin 12, and oxygen sensor ahead of catalytic converter, bank 2, pin 5
DME control module connector A, pin 13, and oxygen sensor ahead of catalytic converter, bank 2, pin 1
DME control module, connector A, pin 14, and oxygen sensor ahead of catalytic converter, bank 2, pin 2
DME control module, connector A, pin 15, and oxygen sensor ahead of catalytic converter, bank 2, pin 6
DME control module, connector A, pin 51 and oxygen sensor ahead of catalytic converter, bank 1, pin 5
DME control module connector A, pin 52, and oxygen sensor ahead of catalytic converter, bank 1, pin 6
DME control module, connector A, pin 70, and oxygen sensor ahead of catalytic converter, bank 1, pin 1
DME control module, connector A, pin 71, and oxygen sensor ahead of catalytic converter, bank 1, pin 2
Diagnosis/troubleshooting
NOTE: The oxygen sensors ahead of the catalytic converter can only be exchanged in naturally aspirated V8 engines. If this fault is recorded for a turbo V8 engine, however, it can only be caused by polarity reversal in the wiring harness (e.g, following accident repairs).
WARNING: Always observe the notes on possible dangers, the warning and caution notes as well as the general instructions in the introduction.
NOTE: Do not use contact spray on the oxygen sensor plug connections, as this may cause irreparable damage to the wiring (blocking the reference air channels).
NOTE: Do not confuse oxygen sensor ahead of catalytic converter and oxygen sensor behind catalytic converter as this will cause implausible fault entries.
Distinguishing feature of both sensors:
Oxygen sensor in front of catalytic converter (LSU) has a six-I pin connector
Oxygen sensor behind catalytic converter (LSF) has a four pin connector
NOTE: The diagnosis detects contrary adaptation values for oxygen sensor if the adaptation values reach the control limits in opposite directions, interchanged oxygen sensors will be detected.
