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P2431



DTC P2431

Diagnostic Instructions

- Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
- Review Strategy Based Diagnosis for an overview of the diagnostic approach.
- Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC P2431: Secondary Air Injection (AIR) System Pressure Sensor Performance.

Diagnostic Fault Information






Typical Scan Tool Data

AIR Pressure Sensor






Circuit/System Description

The secondary air injection (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 secondary AIR injection 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 solenoid valve relay supplies the current needed to operate the AIR 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.

The AIR diagnostic uses 3 phases to test the AIR system:
1. DTCs P0411 and P2430 run during Phase 1.
2. DTCs P2430 and P2440 run during Phase 2.
3. DTC P2444 runs during Phase 3.

During phase 1, both the AIR pump and the solenoid valve are activated. Normal secondary air function occurs. Expected system pressure is 8-10 kPa above barometric pressure (BARO).

During phase 2, only the AIR pump is activated. The solenoid valve is closed. Pressure sensor performance and solenoid valve deactivation are tested. Expected system pressure is 20-25 kPa above BARO.

During phase 3, neither the AIR pump nor the solenoid valve is activated. AIR pump deactivation is tested. Expected system pressure equals BARO.

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM can detect faults in the AIR pump, AIR solenoid valve/pressure sensor assembly, and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

Conditions for Running the DTC

- DTCs P0106, P0107, P0108, P0412, P0418, P0606, P1635, P1639, 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 that the difference between the AIR pressure sensor and the BARO sensor signals is greater than 10 kPa when the AIR pump is commanded OFF.
OR
- The PCM determines that 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

DTC P2431 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P2431 is a Type B DTC.

Circuit/System Verification

1. Ignition ON, verify that the AIR pump is not activated.
2. Ignition ON, observe that the AIR Pressure Sensor parameter approximately equals the BARO parameter.
-> If not equal, verify that the BARO parameter reading is correct for your altitude. Refer to Altitude Versus Barometric Pressure . If the reading is not correct for your altitude, diagnose the MAP sensor. Refer to DTC P0106 . If the BARO parameter is correct for your altitude, proceed with Circuit/System Testing.
3. Engine running, enable the AIR solenoid with a scan tool and observe that the AIR Pressure Sensor parameter equals approximately 8-10 kPa above BARO.
-> If less than the specified range, verify that the AIR pump is activating. If AIR pump activation is normal, proceed with Circuit/System Testing.

Circuit/System Testing

Important: The Circuit/System Verification must be performed first or misdiagnosis may result.

1. Ignition OFF, disconnect the harness connector at the AIR solenoid valve.
2. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit terminal 1 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 control module.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.
-> If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
-> If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module.
4. Verify the scan tool AIR Pressure Sensor parameter is less than 0.5 volts.
-> If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the control module.
5. Install a 3A fused jumper wire between the signal circuit terminal 2 and the 5-volt reference circuit terminal 3. Verify the scan tool AIR Pressure Sensor parameter is greater than 4.9 volts.
-> If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the control module.
6. Connect all electrical connectors.
7. Ignition ON, engine OFF, observe the AIR Pressure Sensor parameter.
-> If the AIR Pressure Sensor parameter does not equal the BARO parameter, replace the AIR solenoid valve.
8. Engine RUNNING, enable the AIR solenoid valve with a scan tool and observe that the AIR Pressure Sensor parameter equals approximately 8-10 kPa above BARO.
-> If not within the specified range, continue with this procedure.
9. Remove the AIR inlet hose from the AIR pump.
10. Engine RUNNING, enable the AIR solenoid valve with a scan tool and observe that the AIR Pressure Sensor parameter increases to 8-10 kPa above BARO.
-> If within the specified range, the AIR pump inlet hoses/pipes are restricted. Remove the restriction or replace the hose/pipe.
-> If not within the specified range, continue with this procedure.
11. Disconnect the hose from the AIR pump outlet.
12. Disconnect the hose quick-connect from the AIR solenoid valve inlet.
13. Install a length of standard 1 inch I.D. (25.4 mm) hose from the AIR pump outlet to the AIR solenoid valve inlet.
14. Engine RUNNING, enable the AIR solenoid valve with a scan tool and observe that the AIR Pressure Sensor parameter increases to 8-10 kPa above BARO.
-> If within the specified range, the AIR pump outlet hoses/pipes are restricted or leaking. Remove the restriction or replace the hose/pipe.
-> If less than the specified range, replace the AIR pump.
-> If more than the specified range, continue with this procedure.
15. Remove the AIR solenoid valve.
16. Leave the standard hose and harness connector connected.
17. Engine RUNNING, enable the AIR solenoid valve with a scan tool and observe that the AIR Pressure Sensor parameter increases to approximately 7 kPa above BARO.
-> If more than the specified range, replace the AIR solenoid valve.
-> If within the specified range, test/inspect the cylinder head for restriction.

Component Testing

Solenoid Valve

Apply fused battery voltage and ground to the solenoid and verify that the valve opens and closes completely as voltage is applied to and removed from the solenoid. Observe that the valve is not obstructed or leaking.
-> If the valve operates incorrectly, leaks, or is obstructed, remove the obstruction or replace the valve.

Repair Verification

1. With the key ON and the engine OFF, observe that the AIR Pressure Sensor parameter is approximately equal to BARO.
2. With the engine running, enable the AIR pump with a scan tool and observe that the AIR Pressure Sensor parameter equals approximately 20-25 kPa above BARO.
3. With the engine running, enable the AIR Solenoid with a scan tool and observe that the AIR Pressure Sensor parameter equals approximately 8-10 kPa above BARO.
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