HO2S Heater Control Circuit High (Bank 1 Sensor 2)
Code P0038 means the heater control circuit for Bank 1 Sensor 2 (downstream O2 sensor) is reading high voltage — above expected range when the heater is commanded on. This indicates an open in the ground circuit or a short to voltage in the heater wiring.
What You Might Notice
- Check engine light on
- Catalyst monitor may not complete
- May fail emissions test
Most Common Causes
- 1
Open heater ground circuit (Bank 1 Sensor 2)
The ground return for the heater circuit is broken, causing high voltage.
- 2
Short to voltage in heater wiring
Harness contact with a power source pulls the circuit high.
- 3
Open heater element inside sensor
An open coil causes high circuit voltage when the PCM commands the heater on.
How to Diagnose It
- 1
Check Open heater ground circuit (Bank 1 Sensor 2) — The ground return for the heater circuit is broken, causing high voltage.
- 2
Check Short to voltage in heater wiring — Harness contact with a power source pulls the circuit high.
- 3
Check Open heater element inside sensor — An open coil causes high circuit voltage when the PCM commands the heater on.
How to Fix It
- 1
Check heater ground circuit continuity
Verify ground return is intact — open ground causes high voltage.
- 2
Inspect wiring for shorts to voltage
Trace harness near the catalytic converter.
- 3
Test heater element resistance
Open reading (OL) confirms failed sensor.
- 4
Replace Bank 1 Sensor 2 O2 sensor
Install OEM-quality replacement.
- 5
Clear and verify
Confirm resolution after a drive cycle.
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