P0030Powertrain
Powertrain · SAE
O2 Sensor Heater Circuit — Bank 1, Sensor 1
Meaning
The ECU has detected an electrical fault in the heater circuit of the upstream (pre-catalyst) oxygen sensor on bank 1. The sensor's internal heater element is not receiving adequate current or the circuit is open, preventing the sensor from reaching its optimal operating temperature quickly.
Common causes
- Broken internal heater element inside the O2 sensor
- Open or corroded wiring/connector on the heater supply line
- Blown heater circuit fuse
- Short to ground in the heater wiring
- Faulty heater relay
- Rare ECU internal driver failure
Symptoms
- Check engine light (MIL) on
- Increased fuel consumption, especially on short cold trips
- Prolonged open-loop fuelling during warm-up
- Possible rough idle during cold start phase
- Elevated CO/HC at emissions test
Severity
Moderate: the engine remains driveable but the sensor operates in open loop longer than normal, increasing emissions and fuel consumption until it self-heats by exhaust convection.
What to do
- Measure heater element resistance at sensor connector pins (typical 2–30 Ω cold; infinite = replace sensor)
- Check for 12 V supply and good ground at the heater connector with ignition ON
- Inspect wiring harness from sensor to ECU for breaks, chafing, or corroded connectors
- Check the dedicated O2 heater fuse
- If wiring is intact, replace the O2 sensor B1S1