P0040 Volvo 1/1 And 2/1 O2 Sensor Harness Connectors Reversed

Possible causes

– 1/1 And 2/1 O2 sensors harness is open or shorted
– 1/1 And 2/1 O2 sensors circuit connectors (wrong connection)
– Faulty Powertrain Control Module (PCM)

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0040 Volvo Description

At ignition on the Powertrain Control Module (PCM) checks the voltage on the ground side of the O2 sensor harness connector. If voltage is higher than two volts the P0040 Volvo code will set.