P0150: oxygen sensor circuit malfunction, bank 2, sensor 1. Meaning, possible causes and checks before replacement.
Meaning, symptoms, causes and checks
P0150 indicates a circuit or signal-function abnormality for bank 2, sensor 1. This is the upstream sensor used for mixture control. The code alone does not identify the sensor, wiring or operating condition as the cause.
Affected system: Powertrain
Symptoms
- Engine warning lamp and a stored code.
- Higher fuel use or uneven running if mixture control is disturbed.
Possible causes
- Open or shorted circuit, damaged terminals or a disconnected connector.
- Damaged sensing element; unsuitable heating or mixture conditions.
What to check
- Confirm B2S1 in the engine diagram and save related codes and freeze-frame data before clearing anything.
- With the exhaust cold, inspect the B2S1 harness for melted insulation, rubbing, water in the connector and loose terminals.
- Identify conventional versus wideband operation; check signal, return and heating using the diagram for that system.
- For an A/F sensor, test the pump and reference circuits separately using the OEM diagram; do not treat its signal as conventional oxygen sensor voltage.
- After correcting the confirmed fault, repeat the OEM monitor conditions and check for code recurrence, beyond merely extinguishing the lamp.
Also written as: P0150-00, P015000, PO150 (some scan tools add the fault-type byte, e.g. -00).