P0138
DTC P0131, P0132, P0137, or P0138
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0131
- HO2S Circuit Low Voltage Sensor 1
DTC P0132
- HO2S Circuit High Voltage Sensor 1
DTC P0137
- HO2S Circuit Low Voltage Sensor 2
DTC P0138
- HO2S Circuit High Voltage Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
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. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The control module supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the control module operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.
Conditions for Running the DTC
P0131 and P0137
* DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
* The system voltage is between 10-18V.
* The scan tool special functions are not active
* The Air Fuel Ratio parameter is between 0.9-1.1.
* The TP Indicated Angle parameter is between 3-45 percent.
* The Loop Status parameter is closed.
* The ECT parameter is less than 131°C (268°F).
* All fuel injectors are ON.
* The traction control is not active.
P0132 and P0138
* DTCs P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
* The system voltage is between 10-18V.
* The scan tool special functions are not active.
* The TP Indicated Angle parameter is between 3-45 percent.
* The Air Fuel Ratio parameter is between 0.9-1.1.
* The above conditions must be met for at least 3 seconds.
Conditions for Setting the DTC
P0131
* The control module detects that the HO2S 1 signal voltage is less than 50 mV for more than 25 seconds.
* This diagnostic runs continuously.
P0132
* The control module detects that the HO2S 1 signal voltage is more than 1,050 mV for more than 20 seconds.
* This diagnostic runs continuously.
P0137
* The control module detects that the HO2S 2 signal voltage remains below 50 mV for more than 120 seconds.
* This diagnostic runs continuously.
P0138
* The HO2S 2 voltage is more than 1,050 mV for longer than 96 seconds.
* This diagnostic runs continuously.
Action Taken When the DTC Sets
DTCs P0131, P0132, P0137, and P0138 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0131, P0132, P0137, and P0138 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
* Heated Oxygen Sensor Wiring Repairs (Heated Oxygen Sensor Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. If any HO2S heater DTCs are set, perform those diagnostics first.
2. Allow the engine to reach operating temperature.
3. Engine running, observe the affected HO2S parameter with a scan tool.
• The pre-catalyst oxygen sensor value should vary from below 200 mV to above 800 mV and respond to fueling changes.
• The post-catalyst oxygen sensor value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.
4. The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:
Caution: Refer to Silicon Contamination of Heated Oxygen Sensors Caution (Silicon Contamination of Heated Oxygen Sensors Caution).
* A silicon contaminated HO2S
* Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-in-Fuel Diagnosis)
* Engine oil consumption-Refer to Oil Consumption Diagnosis (Oil Consumption Diagnosis).
* Engine coolant consumption-Refer to Loss of Coolant (Loss of Coolant).
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
Note: All modules must be powered down or misdiagnosis may result.
1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
2. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
3. Ignition OFF, measure for less than 5 ohm between the appropriate HO2S low signal circuit terminal A and ground.
• If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the engine control module (ECM).
4. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
• If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
• If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
5. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and the battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
• If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
6. If all circuits test normal, replace the appropriate HO2S.
Repair Instructions
Caution: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution (Heated Oxygen Sensor Resistance Learn Reset Caution).
Note: For DTC P0131 and P0132, in order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the Conditions for Running and Setting DTC P0420 and verify that P0420 runs and passes. Refer to DTC P0420 (P0420).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Sensor 1 (Heated Oxygen Sensor Replacement - Sensor 1)
* Heated Oxygen Sensor Replacement - Sensor 2 (Heated Oxygen Sensor Replacement - Sensor 2)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming