Powertrain
generic / SAE
P2A09
O2 Sensor Negative Voltage Bank 2 Sensor 1
The ECM detects a negative voltage on the signal line of oxygen sensor 1 on bank 2. This is unusual for narrow-band sensors and often indicates a short to a negative reference, ground offset, or a wide-band sensor wired incorrectly.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / numberA / 09
Possible causes
- Signal wire shorted to negative reference high
- Ground offset between sensor and ECM medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 100–600 €
- Estimated time: 0.5–3 h
- Component: oxygen sensor b2s1
- Component: wiring harness
- Component: ecm
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012