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)

Symptoms

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

P0040 Description

O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1 is the generic definition for the P0040; however your vehicle’s manufacturer may have a different definition and information for the P0040 code.

P0040 Information for specific makes

P0040 AUDI
P0040 BMW
P0040 CHRYSLER
P0040 DODGE
P0040 FORD
P0040 JEEP
P0040 MAZDA
P0040 VOLKSWAGEN