P2A00
DTC P2A00
CIRCUIT DESCRIPTION
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 vehicle 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 approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,100 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 1,100 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 within each HO2S heat the sensor. This allows the system to enter Closed Loop earlier and the control module to calculate air-to-fuel ratio quicker.
If the powertrain control module (PCM) detects an active HO2S 1 signal of a lower than calibrated minimum amplitude, DTC P2A00 will set.
The HO2S 1 has the following circuits:
- A HO2S 1 high signal circuit
- A HO2S 1 low reference circuit
- A HO2S 1 heater ignition voltage circuit
- A HO2S 1 heater low control circuit
DTC DESCRIPTOR
This diagnostic procedure support the following DTC:
DTC P2A00 HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 1
CONDITIONS FOR RUNNING THE DTC
- DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P1133, P1134 are not set.
- The Engine Run Time parameter is at least 3 minutes.
- The MAF sensor parameter is between 5-38 g/s.
- The Engine Speed parameter is between 602-3,000 RPM.
- The TP sensor parameter is between 3-35 percent.
- The ECT sensor parameter is more than 65°C (149°F).
- The system voltage is between 9-18 volts.
- Traction control is not active.
- Decel Fuel Cutoff parameter is Not Active.
- Power Enrichment (PE) parameter is Not Active.
- The above conditions have been met for at least 3 seconds.
CONDITIONS FOR SETTING THE DTC
- The HO2S 1 voltage remains within 300 mV to 600 mV range for 300 out of 360 samples. each sample is 100 ms
- The PCM detects HO2S 1 voltage signal remains within 300 mV to 600 mV range for more than 3.6 seconds.
- This diagnostic runs continuously.
ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.
TEST
