P0038
DTC P0038
DTC DESCRIPTORS
DTC P0031
HO2S Heater Control Circuit Low Voltage Sensor 1
DTC P0032
HO2S Heater Control Circuit High Voltage Sensor 1
DTC P0037
HO2S Heater Control Circuit Low Voltage Sensor 2
DTC P0038
HO2S Heater Control Circuit High Voltage Sensor 2
DIAGNOSTIC FAULT INFORMATION
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection
CIRCUIT DESCRIPTION
The heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module.
The HO2S utilizes the following circuits:
- A signal circuit
- A low reference circuit
- An ignition 1 voltage circuit
- A heater control circuit
CONDITIONS FOR RUNNING THE DTC
- The engine is running.
- The ignition 1 voltage is between 7.5-16 volts.
- The DTC runs continuously when the above conditions are met.
CONDITIONS FOR SETTING THE DTC
The engine control module (ECM) detects an open, short to ground or voltage on the control circuit of the HO2S.
ACTION TAKEN WHEN THE DTC SETS
DTC P0031, P0032, P0037, and P0038 are Type A DTCs.
CONDITIONS FOR CLEARING THE MIL/DTC
DTC P0031, P0032, P0037, and P0038 are Type A DTCs.
CIRCUIT/SYSTEM VERIFICATION
1. With the engine at normal operating temperature, operate the engine above 1,200 RPM for 30 seconds and then allow the engine to idle. DTC P0031, P0032, P0037, or P0038 should not set.
IMPORTANT: It may take up to 8 minutes for the DTC to set.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.
CIRCUIT/SYSTEM TESTING
1. Ignition OFF, disconnect the harness connection OFF, disconnect the harness connector of the HO2S.
2. Connect a test lamp between the ignition 1 voltage circuit of the HO2S heater and the negative terminal of the battery.
IMPORTANT: The test lamp is used to load the circuit and may not illuminate.
3. Ignition ON, test for less than 0.1 volt between the ignition 1 voltage circuit of the HO2S heater and the positive terminal of the battery.
- If greater than 0.1 volt, test the ignition 1 voltage circuit of the HO2S heater for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the HO2S sensor.
4. Ignition OFF, connect a test lamp between the control circuit of the HO2S heater and the positive terminal of the battery.
- If test lamp illuminates, test the control circuit of the HO2S heater for a short to ground. If the circuit/connections test normal, replace the ECM.
5. Ignition ON, test for less than 0.3 volt between the control circuit of the HO2S heater and the negative terminal of the battery.
- If greater than 0.3 volt, test the control circuit of the HO2S heater for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.
6. If all circuits/connections test normal, test or replace the HO2S sensor.
COMPONENT TESTING
1. Ignition OFF, disconnect the harness connector of the HO2S.
2. Measure for 3-35 ohms of resistance between the ignition 1 voltage circuit terminal and the control circuit terminal of the HO2S heater.
- If the resistance is out of the specified range, replace the HO2S sensor.
REPAIR INSTRUCTIONS
Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests