P2431

DTC P2431 (WITH RPO CODE NU3)

SYSTEM DESCRIPTION
The DTC P2431 secondary air injection (AIR) system pressure sensor performance diagnostic monitors the accuracy of the sensor signal. The AIR system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the AIR pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground, and a signal circuit. By comparing the measured pressure against the expected pressure, the PCM can detect faults in the AIR pump, the AIR control/shut-off valve, and the exhaust check valve. The pressure sensor can also detect leaks in the AIR system plumbing.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
- DTC P2431 Secondary Air Injection (AIR) System Pressure Sensor Performance

CONDITIONS FOR RUNNING THE DTC
- DTCs P0107, P0108, P0412, P0418, P0606, P0641, P0651, P2432, P2433 are not set.
- The ignition is ON.
- DTC P2431 runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC
The PCM determines the difference between the AIR pressure sensor and the barometric pressure (BARO) sensor signals is greater than 10 kPa when the AIR pump is commanded OFF.
OR
The PCM determines the difference between the AIR pressure sensor and the BARO sensor signals is greater than 50 kPa when the AIR pump is commanded ON.

ACTION TAKEN WHEN THE DTC SETS
- The PCM illuminates the malfunction indicator lamp (MIL).
- The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC
- The PCM illuminates the MIL.
- A DTC will clear the 40 consecutive warm-up cycles have occurred without a fault.
- A DTC can be cleared by using the scan tool Clear Information function.

DIAGNOSTIC AIDS
- This DTC may set due to an incorrect manifold absolute pressure (MAP)/ BARO value caused by a faulty MAP sensor. Before replacing any component ensure that this condition does not exist.
- An intermittent malfunction may be caused by a fault in an AIR pressure sensor electrical circuits. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions
- If the DTC cannot be duplicated, the information included in the Freeze Frame can be useful in determining vehicle operating conditions when the DTC was first set.

TEST DESCRIPTION

Steps 1 - 7:

Steps 8 - 15:

The numbers below refer to the step numbers on the diagnostic table.
3. If the AIR pump is always ON, DTC P2431 can set. DTC P2444 will locate and repair the cause of an AIR pump stuck in the ON position.
4. This step determines if DTC P2431 is the result of a hard failure or an intermittent condition. Normal pressure sensor input voltage is approximately 2.6 volts with the ignition ON, the engine OFF, and the AIR pump OFF.
7. This step inspects for excessive resistance in the reference voltage circuit. If the test lamp does not illuminate at all, there is resistance in the circuit.
9. This step tests for high electrical resistance in the AIR pressure sensor circuit.
10. This step tests for high electrical resistance in the AIR pressure sensor low reference circuit.