P0031

HO2S Heater Control Circuit Low Voltage (Bank 1 Sensor 1)

Q: What does fault code P0031 mean?

HO2S Heater Control Circuit Low Voltage (Bank 1 Sensor 1). The ECM has detected that the heater control circuit voltage for the Bank 1 upstream oxygen sensor is below the normal range, typically indicating a short to ground.

Q: What are the possible causes of P0031?

Oxygen sensor heater coil shorted to ground; Wiring harness insulation damaged causing short to ground; ECM internal driver transistor shorted to ground.

Severity: Medium Fuel & Air Metering Generic Code

Detailed Description

The ECM has detected that the heater control circuit voltage for the Bank 1 upstream oxygen sensor is below the normal range, typically indicating a short to ground.

Possible Causes

Oxygen sensor heater coil shorted to ground

Wiring harness insulation damaged causing short to ground

ECM internal driver transistor shorted to ground.

Solutions & Repair Guide

Disconnect the oxygen sensor connector and measure the resistance from the harness-side heater control terminal to ground — it should be greater than 1 megaohm; If the harness is normal, replace the oxygen sensor.

Disclaimer: The information above is for reference only and does not constitute professional repair advice. Actual causes may vary depending on vehicle make, model, year, and configuration. Always consult a qualified technician for accurate diagnosis.