System Description
The DTC P2431 Secondary Air Injection (AIR) System Pressure Sensor Performance diagnostic monitors the accuracy of the sensor signal. The secondary AIR system helps reduce exhaust emissions. 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 shut-off valve. The AIR shut-off valve controls the flow of air from the AIR pump to the exhaust manifold. The AIR solenoid valve supplies the manifold vacuum that is used to operate the AIR shut-off valve. A pressure sensor is used to monitor the air flow from the AIR pump. The PCM supplies the pressure sensor with a 5-volt reference, an electrical ground, and a signal return circuit that has a 5-volt bias. By comparing the measured pressure against the expected pressure the pressure sensor can detect faults in the AIR pump, AIR shut-off valve, and the AIR solenoid valve. The pressure sensor can also detect leaks in the secondary AIR system plumbing.
Conditions for Running the DTC
| • | The engine is running. |
| • | DTC P2431 runs continuously once the above condition has been met. |
Conditions for Setting the DTC
| • | Condition 1--The pressure sensor determines that the AIR system pressure is higher or lower than expected when the AIR pump is ON. |
| • | Condition 2--The pressure sensor determines that the AIR system pressure is higher or lower than expected when the AIR pump is OFF. |
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 MIL turns OFF after 3 consecutively passing trips without a fault present. |
| • | A DTC will clear after 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
| • | 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 . |
| • | If the DTC cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set. |
| • | Operating the vehicle in Check Mode will increase the ability of the powertrain control (PCM) module to detect engine control system malfunctions. Refer to Check Mode in Service Bay Test . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
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If the AIR pump is always ON, DTC P2431 can set. DTC P2444 will locate and repair the cause of a stuck ON AIR pump.
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This step determines if DTC P2431 is the result of a hard failure or an intermittent condition. Normal pressure sensor input voltage is approximately 1.6 volts with the ignition ON, AIR pump OFF.
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This step determines if there is trapped pressure at the AIR pressure sensor.
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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.
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This step checks for high electrical resistance in the AIR pressure sensor input circuit.
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This step checks for high electrical resistance in the AIR pressure sensor ground circuit.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||
Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | ||||||
Is the secondary AIR pump ON? | -- | Go to DTC P2444 | Go to Step 3 | |||||
Is the pressure sensor input circuit voltage within the specified value? | 1.5-1.6 V | Go to Step 4 | Go to Step 5 | |||||
4 |
Did the pressure sensor voltage increase to at least the specified value when the AIR pump was ON? | 1.9-2.1 V | Go to Diagnostic Aids | Go to Step 7 | ||||
Disconnect the pressure sensor hose. Is the pressure sensor input circuit voltage within the specified value? | 1.5-1.6 V | Go to Step 6 | Go to Step 7 | |||||
6 | Repair the cause of the trapped air pressure in the AIR system. Did you complete the repair? | -- | Go to Step 15 | -- | ||||
7 |
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 8 | ||||
Does the test lamp illuminate at least dimly? | -- | Go to Step 9 | Go to Step 13 | |||||
9 | Measure the voltage of the AIR pressure sensor input circuit on the harness side using a DMM. Is the voltage near the specified value? | 4.9 V | Go to Step 11 | Go to Step 10 | ||||
Was a repair necessary? | -- | Go to Step 13 | Go to Step 14 | |||||
Did you find and correct a condition? | -- | Go to Step 15 | Go to Step 12 | |||||
12 | Replace the AIR pressure sensor. Refer to Secondary Air Injection Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||
13 | Repair the high resistance in the reference voltage circuit of the AIR pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- | ||||
14 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||
15 |
Did a DTC P2431 set? | -- | Go to Step 2 | Go to Step 16 | ||||
16 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||
