The heated oxygen sensor 2 (HO2S-2) is located behind the catalytic converter. The sensor is used by the powertrain control module (PCM) to determine the oxygen storage capability of the catalytic converter. Due to the location of the HO2S-2, a heater element is required to provide additional heat which speeds up sensor activation time. The PCM will command the heater ON (supply ground path) after the first 45 seconds of engine run time and will not turn it OFF until the engine is turned OFF. The PCM monitors the heater current draw and will set DTC P0038 when the heater is commanded ON and the current draw into the PCM is too high.
DTC Parameters
DTC P0038 will set if HO2S-2 heater current is greater than 2.26 amps with heater commanded ON when:
| • | The condition exists for longer than 0.5 seconds. |
| • | The battery voltage is greater than 10.9 volts for longer than 0.5 seconds. |
| • | The engine run time is greater than 45 seconds. |
DTC P0038 runs continuously after the first 45 seconds of engine run time when heater is commanded ON.
DTC P0038 is a type B DTC.
Diagnostic Aids
To locate an intermittent problem, use a scan tool to monitor HO2S HEATER - HIGH VOLT test after engine has been running over 45 seconds. When a fault (short to voltage or shorted solenoid) exists, the scan tool will display TEST FAIL.
The test updates every 100 ms whenever the engine is running over 45 seconds and the device is being commanded ON via the PCM.
The heater element resistance is 12-27 ohms.
