Powertrain
generic / SAE
P0040
O2 Sensor Signals Swapped Bank 1 Sensor 1/Bank 2 Sensor 1
The pre-cat oxygen sensors of bank 1 and bank 2 appear to be wired the wrong way around — bank 1 reacts when bank 2 should and vice versa. Typically after recent service.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number– / 40
Possible causes
- Sensors swapped after recent replacement high
- Wiring harness routed across banks medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Inspection / repair
- Difficulty: easy
- DIY: possible
- Estimated cost: 10–100 €
- Estimated time: 0.3–1 h
- Component: oxygen sensor b1s1
- Component: oxygen sensor b2s1
- Component: sensor wiring
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012