P0050Powertrain
Powertrain · SAE
O2 Sensor Heater Circuit — Bank 2, Sensor 1
Meaning
The ECU detected an electrical fault in the heater circuit of the upstream (pre-catalyst) oxygen sensor on bank 2, the cylinder bank that does not contain cylinder number 1. The heater fails to bring the sensor to operating temperature within the expected time window.
Common causes
- Broken internal heater element in the O2 sensor B2S1
- Open or corroded wiring/connector on the bank 2 heater supply line
- Blown O2 heater fuse
- Short to ground in the heater wiring
- Faulty heater relay
- Rare ECU driver fault
Symptoms
- Check engine light (MIL) on
- Increased fuel consumption during short cold trips
- Prolonged open-loop fuelling on bank 2
- Possible rough idle during cold start
- Elevated CO/HC emissions
Severity
Moderate: the engine is driveable but bank 2 mixture control is not optimised during warm-up, increasing emissions and fuel consumption.
What to do
- Measure heater resistance at connector pins (typical 2–30 Ω; open = replace sensor)
- Check 12 V supply and ground at B2S1 heater connector with ignition ON
- Inspect wiring to ECU for damage, chafing, or corrosion
- Check the O2 heater fuse
- Replace O2 sensor B2S1 if external wiring is intact