P0150Powertrain
Powertrain · SAE
O2 Sensor Bank 2 Sensor 1 – Circuit Fault
Meaning
The upstream lambda sensor on Bank 2 has a general circuit fault — voltage is out of range or the signal detected by the ECU is implausible. The code indicates an electrical anomaly without specifying whether voltage is high or low.
Common causes
- Defective upstream O2 sensor (signal out of range or absent)
- Open circuit or short in the wiring between sensor and ECU
- Damaged, corroded connector or loose terminals
- Missing or incorrect heater supply voltage
- Internal ECU fault on the B2S1 sensor acquisition channel
Symptoms
- MIL (Check Engine) warning light on
- Engine operating in open-loop mode (ECU ignores lambda signal)
- Increased fuel consumption
- Elevated CO, HC, and NOx emissions
- Possible rough idle or reduced throttle response
Severity
Moderata: The fault disables closed-loop fuelling control on Bank 2, resulting in fixed mixture enrichment, higher fuel consumption, and out-of-spec emissions.
What to do
- Read all DTCs and live data; verify whether the ECU receives a plausible signal from sensor B2S1 with the engine at operating temperature.
- Measure heater supply voltage (typically +12V) and check heater ground circuit continuity.
- Check signal wire continuity and insulation from sensor to ECU.
- Inspect connector B2S1 for oxidation, moisture, or bent terminals.
- Replace the upstream O2 sensor B2S1 if the circuit is electrically intact but the signal remains abnormal; consult technical documentation before ruling out an ECU fault.