P0030 Code – HO2S Heater Control Circuit


Bank 1, sensor 1 of the O2 sensor heater circuit is faulty. As such, the engine isn’t achieving closed loop and therefore the car has increased emissions.

Main Symptoms:

  • Check Engine Light comes on
  • Longer time needed to achieve closed loop
  • Decreased fuel economy
  • Engine may go into fixed fuel mix

Possible Causes:

The P0030 code might be an indication of the ECM not getting the correct signal
The P0030 trouble code can happen when the correct signal is sent to the ECM
  • H02S sensor in bank 1, circuit 1 is not sending the correct signal to ECM
  • Damaged or failed element in heater circuit
  • Open in O2 sensor heater’s circuit
  • Open/short in O2 sensor heater’s battery
  • Defective ECM (this is the least likely cause)

Diagnostic Steps:

  • Inspect wiring and power to the O2 sensor and ensure there’s no damage/open/short
  • Use code reader to pull engine codes
  • Check voltage of O2 sensor and ensure it matches manufacturer’s specs
  • Replace O2 sensor if necessary

Read More: How to Use an OBD-II Scan Tool to Diagnose Your Car