Without Variable Camshaft Phasing
DTC P0131, P0132, P0134, P0137, P0138, or P0140
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) 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 P0134
- HO2S Circuit Insufficient Activity Sensor 1
DTC P0137
- HO2S Circuit Low Voltage Sensor 2
DTC P0138
- HO2S Circuit High Voltage Sensor 2
DTC P0140
- HO2S Circuit Insufficient Activity Sensor 2
Diagnostic Fault Information
Typical Scan Tool Data
Circuit 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. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. 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 above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage 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.
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
* DTCs P0031, P0032, P0037, P0038, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0135, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0217, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0313, P0335, P0336, P0337, P0351, P0352, P0401, P0402, P0404, P0405, P0406, P0443, P0458, P0459, P0488, P0496, P0502, P0506, P0507, P0562, P0563 and P2110 are not set.
* The engine has been operating for greater than 60 seconds.
* The calculated airflow into the engine is greater than 9 g/s.
* The engine coolant temperature is greater than 60°C (140°F).
* The ignition 1 voltage is greater than 10 volts.
* The fuel system is in Closed Loop.
* The vehicle is not decelerating.
* The DTCs run continuously when the above conditions are met for 3 seconds.
Conditions for Setting the DTC
DTC P0131 or P0137
The engine control module (ECM) detects that the HO2S 1 voltage is less than 50 mV.
DTC P0132 or P0138
The ECM detects that the HO2S 1 voltage is greater than 950 mV.
DTC P0134 or P0140
The ECM detects that the HO2S 1 voltage is between 299-600 mV.
Action Taken when the DTC Sets
DTCs P0131, P0132, P0134, P0137, P0138, and P0140 are Type B DTCs.
DTCs P0131, P0132, and P0134
The ECM commands open loop fuel control.
Conditions for Clearing the MIL/DTC
DTCs P0131, P0132, P0134, P0137, P0138, and P0140 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Important: In extreme cold weather conditions ice may form in the vacuum source to the MAP sensor and may set a DTC. Inspect the MAP sensor and the vacuum source for ice, moisture, or other restrictions.
1. Ignition ON, observe the scan tool MAP sensor pressure parameter. Start the engine, verify the scan tool MAP sensor pressure parameter changes.
• If the scan tool MAP sensor pressure parameter does not change, refer to DTC P0107 or P0108 (P0107) for further diagnosis.
2. Engine running, observe the scan tool heated oxygen sensor voltage parameters. The reading should fluctuate above and below the range of 350-550 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 harness connector at the applicable HO2S.
2. Ignition OFF, test for less than 5 ohms of resistance between the low reference circuit terminal listed below and ground.
* HO2S 2 (Euro IV) low reference circuit terminal 3
* HO2S 2 (Non Euro IV) low reference circuit terminal 1
• If greater than the specified range, test the low reference circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
3. Engine running, verify the applicable HO2S parameter is between 350-500 mV.
• If less than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Install a 3A fused jumper wire between the signal circuit and the low reference circuit terminals listed below. Engine running, verify the scan tool HO2S parameter is less than 60 mV.
* HO2S 2 (Euro IV) low reference circuit terminal 3
* HO2S 2 (Non Euro IV) low reference circuit terminal 1
* HO2S 2 (Euro IV) signal circuit terminal 1
* HO2S 2 (Non Euro IV) signal circuit terminal 2
• If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. Verify none of the following conditions exist:
* Lean or rich fuel injectors-Refer to Fuel Injector Balance Test with Special Tool (Fuel Injector Balance Test with Special Tool).
* Water intrusion in the HO2S harness connector
* Low or high fuel system pressure-Refer to Fuel System Diagnosis (Fuel System Diagnosis).
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Alcohol/Contaminants-in-Fuel Diagnosis).
* Fuel saturation of the evaporative emission (EVAP) canister
* Exhaust leaks near the HO2S
* Engine vacuum leaks
• If you find any of the above conditions, repair as necessary.
6. If all circuits test normal, test or replace the applicable HO2S.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Sensor 1 (Service and Repair)
* Heated Oxygen Sensor Replacement - Sensor 2 (Service and Repair)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming