P0156Powertrain
Powertrain · SAE
O2 Sensor Circuit Malfunction — Bank 2, Sensor 2
Meaning
The downstream oxygen sensor on Bank 2 (the bank not containing cylinder 1) is producing a signal that is out of range or implausible. The voltage detected by the ECU does not fall within the expected operating values for a post-catalyst monitoring sensor.
Common causes
- Faulty or out-of-calibration O2 sensor (Bank 2, Sensor 2)
- Damaged, oxidised, or broken wiring in the sensor circuit
- Loose, corroded, or damaged O2 sensor connector
- Short circuit in the signal circuit to ground or to supply voltage
- Open or short-circuited internal heater element within the sensor
- Internal fault in the ECU sensor-reading circuit
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Possible increase in fuel consumption
- Catalyst efficiency monitoring compromised
- No noticeable driveability symptoms in many cases
Severity
Moderata: The vehicle is generally driveable, but the emissions control system is not functioning correctly and the catalyst is not being monitored; prompt attention prevents secondary damage.
What to do
- Visually inspect the wiring harness and connector of O2 sensor Bank 2 Sensor 2 for damage, corrosion, or looseness
- Measure sensor supply voltage and ground connection with a multimeter
- Check the resistance of the sensor heater circuit; replace the sensor if out of specification
- Perform live data monitoring with a scan tool at operating temperature to verify the sensor signal
- Replace the O2 sensor if the circuit is intact but the signal remains anomalous