P2A01
DTC P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A00, P2A01, P2A03, or P2A04
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 Bank 1 Sensor 1
DTC P0132
- HO2S Circuit High Voltage Bank 1 Sensor 1
DTC P0137
- HO2S Circuit Low Voltage Bank 1 Sensor 2
DTC P0138
- HO2S Circuit High Voltage Bank 1 Sensor 2
DTC P0151
- HO2S Circuit Low Voltage Bank 2 Sensor 1
DTC P0152
- HO2S Circuit High Voltage Bank 2 Sensor 1
DTC P2A00
- HO2S Performance Bank 1 Sensor 1
DTC P2A01
- HO2S Performance Bank 1 Sensor 2
DTC P2A03
- HO2S Performance Bank 2 Sensor 1
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, P0137, P0151, or P0157
* DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, or P2176 are not set.
* The engine is operating in Closed Loop.
* The Ignition 1 voltage is between 10-18 volts.
* The fuel level is greater than 10 percent.
* The throttle position (TP) is between 0-50 percent.
* The DTCs run continuously when the above conditions are met for 3 seconds.
P0132, P0138, P0152, or P0158
* DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, or P2176 are not set.
* The engine is operating in Closed Loop.
* The Ignition 1 voltage is between 10-18 volts.
* The fuel level is greater than 10 percent.
* The throttle position (TP) is between 0-60 percent.
* The DTCs run continuously when the above conditions are met for 3 seconds.
DTCs P2A00 or P2A03
* DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, or P2176 are not set.
* The engine run time is greater than 100 seconds.
* The engine speed is between 500-5,000 RPM.
* The Ignition 1 voltage is between 10-18 volts.
* The mass air flow (MAF) sensor is between 3-50 g/s.
* The engine coolant temperature (ECT) is greater than 70°C (158°F).
* The DTCs run continuously when the above conditions are met for 5 seconds.
DTC P2A01
* DTC P2A01 runs a passive test and intrusive test when the following conditions are met.
* DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, or P2A00 are not set.
Passive Test
- The engine is running.
- The engine run time is less than 260 seconds.
- DTC P2A01 Passive Test runs once per drive cycle when the above conditions are met for 2 seconds.
Intrusive Test
- The Ignition 1 voltage is between 10-18 volts.
- The mass air flow (MAF) sensor is between 0.5-50 g/s.
- The engine speed is between 500-5,000 RPM.
- The vehicle speed is between 24-145 km/h (20-80 mph).
- The short term fuel trim is between +5 and -5 percent.
- DTC P2A01 Intrusive Test runs once per drive cycle when the above conditions are met for 1 second.
Conditions for Setting the DTC
P0131, P0137, P0151, or P0157
* The ECM detects that the HO2S voltage is less than 25 mV.
* The DTCs set within 100 seconds when the above condition is met.
P0132, P0138, P0152, or P0158
* The ECM detects that the HO2S voltage is greater than 950 mV.
* The DTCs set within 100 seconds when the above condition is met.
DTC P2A00 or P2A03
* The control module detects that the Loop Status parameter is open.
* DTC P2A00 or P2A03 sets within 5 seconds when the above condition is met.
DTC P2A01
* The ECM detects that the HO2S 2 did not transition below 299 mV and above 751 mV during the passive test.
* The ECM remains in Open Loop due to the HO2S 2 voltage remaining within 250-600 mV for 10 seconds after the HO2s is at operating temperature.
* DTC P2A01 or P2A04 sets within 5 seconds when the above conditions are met.
* One of the following tests fail once per trip/runs until pass or fail reporting:
- Lean Intrusive Test-The control module detects that the HO2S 2 is greater than 751 mV for 8 seconds.
- Rich Intrusive Test-The control module detects that the HO2S 2 is less than 299 mV for 8 seconds.
- DTC P2A01 or P2A04 sets within 2 minutes when the above conditions are met.
Action Taken When the DTC Sets
DTCs P0131, P0132, P0137, P0138, P0151, P0152, P0158, P2A00, P2A01, and P2A03 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0131, P0132, P0137, P0138, P0151, P0152, P0158, P2A00, P2A01, and P2A03 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)
* Heated Oxygen Sensor Wiring Repairs (Heated Oxygen Sensor Wiring Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing For Intermittent Conditions and Poor Connections)
* Wiring Repairs (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. Ignition ON, observe the DTC information with a scan tool. Verify no HO2S heater DTCs are set.
• If a HO2S heater DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code (DTC) List - Vehicle).
2. Engine running at operating temperature, observe the appropriate HO2S parameter with a scan tool. Verify the following:
* The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.
* The post-catalyst oxygen sensors value should change greater 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.
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 for 1 minute. Disconnect the harness connector at the appropriate HO2S.
2. Ignition OFF, test for less than 5 ohm between the low reference circuit terminal A and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
3. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
• If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
• If greater than the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
4. Ignition ON, install a 3 A fused jumper wire between the signal circuit terminal B and ground. Verify the appropriate scan tool HO2S parameter is less than 60 mV.
• If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
5. 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).
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (Service and Repair)
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 (Service and Repair)
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming