P0131
DTC P0131, P0132, P0137, or P0138 (LAF)
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
The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,275 mV. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases toward 0 mV indicates a lean fuel mixture.
The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
Conditions for Running the DTC
P0131
* DTCs P0106, P0107, P0108, P0201, P0202, P0203, P0204, P0411, P0412, P0418, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496 are not set.
* The Loop Status parameter is Closed.
* The Ignition 1 Signal parameter is between 10-32 V.
* The Fuel Level Sensor parameter is more than 10 %.
* DTC P0131 runs when the above conditions are met for 5 s.
P0132
* DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0201, P0202, P0203, P0204, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496 are not set.
* The Loop Status parameter is Closed.
* The Ignition 1 Signal parameter is between 10-32 V.
* The Fuel Level Sensor parameter is more than 10 %.
* DTC P0132 runs when the above conditions are met for 5 s.
P0137
* DTCs P0106, P0107, P0108, P0201, P0202, P0203, P0204, P0411, P0412, P0418, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496 are not set.
* The Loop Status parameter is Closed.
* The Ignition 1 Signal parameter is between 10-32 V.
* The Fuel Level Sensor parameter is more than 10 %.
* DTC P0137 runs when the above conditions are met for 5 s.
P0138
* DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0201, P0202, P0203, P0204, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496 are not set.
* The Loop Status parameter is Closed.
* The Ignition 1 Signal parameter is between 10-32 V.
* The Fuel Level Sensor parameter is more than 10 %.
* DTC P0138 runs when the above conditions are met for 5 s.
Conditions for Setting the DTC
P0131
* The ECM detects that the HO2S 1 Voltage parameter is less than 50 mV.
* DTC P0131 sets within 50 s when the above condition is met.
P0132
* The ECM detects that the HO2S 1 parameter is more than 1,050 mV.
* DTC P0132 sets within 15 s when the above condition is met.
P0137
* The ECM detects that the HO2S 2 voltage parameter is less than 50 mV.
* DTC P0137 sets within 50 s when the above condition is met.
P0138
* The ECM detects that the HO2S 2 voltage parameter is more than 1,050 mV.
* DTC P0138 sets within 15 s when the above condition is met.
Action Taken When the DTC Sets
DTCs P0131, P0132, P0137, P0138 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0131, P0132, P0137, 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 Views)
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)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the DTC information with a scan tool. Verify no B52 HO2S heater DTCs are set.
• If a B52 HO2S heater DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Engine running, observe the appropriate scan tool B52 HO2S voltage parameter. The reading should be within the range of 50-1,050 mV.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, disconnect the appropriate B52 HO2S harness connector.
2. Ignition ON, observe the appropriate scan tool HO2S voltage parameter. The parameter should display 1.27 V.
• If less than the specified range, test the high and low signal circuits for a short to ground. If both signal circuit test normal, replace the K20 ECM.
3. Ignition ON, test for 2.5-3.0 V between the high signal circuit terminal B and ground.
• If less than the specified range, test the high signal circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.
• If greater than the specified range, test the high signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
4. Ignition OFF, connect a 3 A fused jumper wire between the high signal circuit terminal B and the low signal circuit terminal A.
Note: The low signal circuit is tied to a pull-up circuit within the ECM. A voltage of 0.90-1.10 V on the low signal circuit is normal.
5. Ignition ON, verify the scan tool HO2S parameter displays 0.0 V.
• If greater than the specified range, test the low signal circuit for an open/high resistance or for a short to voltage. If the circuit tests normal, replace the K20 ECM.
6. If all circuits test normal, test or replace the appropriate B52 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 replacement, setup, and programming