P2A01

DTC P2A01: HO2S Performance Sensor 2

Circuit Description
Heated oxygen sensors are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the Engine Control Module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air fuel ratio. The ECM supplies the HO2S with a reference voltage of about 0.45 V. The HO2S generates a voltage within a range of 0 - 1 V that fluctuates above and below bias voltage once in closed loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and then provide an accurate voltage signal.

Conditions for Setting the DTC

(Condition 1)
- No CKP, CMP, MAF, oxygen sensor, EVAP purge solenoid, ECT, TP, fuel system, MAP, misfire faults exist.
- Engine is running.
- Engine coolant temperature is greater than -20 °C

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fail. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF at the end of three consecutive validation cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 warm up cycles without a fault.
- The DTC(s) can be cleared by using the scan tool.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. If the voltage does not change more that the specified value, the condition is present.

Troubleshooting

Step 1-10:

Step 11-22: