P0152Powertrain
Powertrain · SAE
O2 Sensor Bank 2 Sensor 1 – High Voltage
Meaning
The upstream lambda sensor on Bank 2 reports voltage consistently above the normal range (above ~1.2 V), indicating a permanent rich signal. This is the mirror of P0132 but for Bank 2.
Common causes
- Defective upstream O2 sensor with signal stuck high
- Persistently rich mixture on Bank 2 (excessive fuel pressure, stuck-open injectors, faulty MAP/MAF sensor)
- Signal wire short to reference voltage or to +12V
- Sensor contamination from oil or coolant
- Internal ECU leak on the B2S1 sensor read path
Symptoms
- MIL (Check Engine) warning light on
- Long-term fuel trim (LTFT) on Bank 2 strongly negative (fuel reduction)
- Increased fuel consumption
- Pungent fuel smell from exhaust
- Possible dark smoke from exhaust under severe rich condition
Severity
Moderata: The fault disables optimal mixture regulation on Bank 2, increases fuel consumption, and may accelerate catalyst deterioration.
What to do
- Read DTCs and fuel trims (STFT/LTFT) for Bank 2; a strongly negative LTFT indicates a real rich condition, not just a sensor fault.
- Check fuel pressure and injector operation on Bank 2.
- Measure sensor voltage at operating temperature under partial load: must switch between ~0.1 V and ~0.9 V; a fixed high value indicates sensor fault.
- Check signal wire for shorts to supply voltage and verify insulation to ECU.
- Replace the upstream O2 sensor B2S1 if sensor fault is confirmed; correct the rich mixture cause if fuel trims indicate real fuel excess.