HO2S Heater Control Circuit Bank 1 Sensor 1
The Powertrain Control Module (PCM) detected a malfunction in the heater circuit of the upstream oxygen sensor on Bank 1. This means the heater element inside the sensor is not drawing the expected amount of electrical current, preventing the sensor from reaching its operating temperature quickly.
While the vehicle will usually drive normally, the engine may run rich during warmup, leading to decreased fuel economy and potential long-term catalytic converter wear. It should be diagnosed and repaired soon to maintain proper emissions and fuel control.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Decreased fuel economy
- Rough idle during cold starts
- Failed emissions test
- Slight hesitation during engine warmup
Likely causes
- Failed Bank 1 Sensor 1 oxygen sensor (internal heater element failure)
- Damaged, burned, or shorted wiring in the O2 sensor heater circuit
- Corroded, disconnected, or loose electrical connector at the O2 sensor
- Blown O2 sensor heater fuse (if equipped)
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the Bank 1 Sensor 1 O2 sensor wiring and connector.
Look for: Look for melted wires, chafing against the exhaust, or corrosion inside the connector pins.
Check the O2 sensor heater circuit fuse.
Look for: Use a multimeter or test light to verify if the fuse is blown, which indicates a short in the circuit.
Measure the resistance of the O2 sensor heater element.
Look for: Unplug the sensor and use a multimeter across the two heater pins. An open circuit (infinite resistance) or out-of-spec resistance confirms the sensor itself has failed.
Verify power and ground at the O2 sensor harness connector.
Look for: With the key on (engine off), check for 12 volts on the power wire and a good ground. Missing power or ground points to a wiring or PCM issue.
Test the PCM ground control circuit for the heater.
Look for: Use a test light or oscilloscope to verify the PCM is pulsing the ground to the heater circuit during a cold start. No pulse indicates a wiring break to the PCM or a faulty PCM.
This page explains the generic P0030 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
Gear guide: Best OBD2 ScannersRead this code yourself next time — from $20 Bluetooth dongles to bidirectional scan tools.Rather have a pro handle it? Find a vetted local mechanic.