Diagnostic Instructions
DTC Descriptors
DTC P2A00: HO2S Performance Sensor 1
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. 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
• | DTCs P0106, P0107, P0108, P0116, P0117, P0118, P0131, P0132, P0201, P0202, P0203, P0204, P1516, P2101, P2119, or P2176 are not set. |
• | The ignition voltage is between 10-18 volts. |
• | The engine speed is between 1,000-3,400 RPM. |
• | The airflow into the engine is between 4-30 g/s. |
• | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
• | The engine run time is greater than 100 seconds. |
• | The engine is not operating is power enrichment (PE), or decel fuel cut-off (DFCO) mode. |
• | DTC P2A00 runs continuously when the above conditions are met for greater than 5 seconds. |
Conditions for Setting the DTC
The ECM detects that the HO2S 1 voltage is greater than 1,100 mV for greater than 20 seconds after closed loop is enabled.
Action Taken When the DTC Sets
DTC P2A00 is a Type B DTC.
Conditions for Clearing the DTC
DTC P2A00 is a Type B DTC.
Diagnostic Aids
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the DTC information with a scan tool. DTC P0030, P0053, P0131, P0132, P0134, or P0135 should not be set.
- 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
- Engine idling, move the HO2S 1 harness connector and the engine control module (ECM) harness connector while monitoring the HO2S 1 voltage parameter. Verify that the HO2S parameter does not change abruptly while moving the related harnesses.
⇒ | If the HO2S parameter does change abruptly while moving the related harnesses repair the circuit as necessary. |
- Ignition OFF, disconnect the harness connector at the HO2S 1.
- Ignition OFF for 1 minute, test for less than 5 Ω between the low reference circuit terminal 3 and ground.
⇒ | 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. |
- Ignition ON, test for 1.5-2.1 V between the signal circuit terminal 1 and ground.
⇒ | If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. 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. |
- Install a 3 A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 3. Engine running, verify the scan tool HO2S parameter is less than 60 mV.
⇒ | If greater than the specified value, replace the ECM. |
- Verify none of the following conditions exist:
• | Water intrusion in the HO2S harness connector |
• | Fuel saturation of the evaporative emission (EVAP) canister |
⇒ | If you find any of the above conditions, repair as necessary. |
- If all circuits test normal, test or replace the HO2S 1.
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.
Caution: When replacing the HO2S perform the following:
• | A code clear with a scan tool, regardless of whether or not a DTC is set |
• | HO2S heater resistance learn reset with a scan tool, where available |
Perform the above in order to reset the HO2S resistance learned value and avoid possible HO2S failure.