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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2006 🢒 Vibe - FWD 🢒 Restraints 🢒 SIR 🢒 DTC P2431

System Description

The DTC P2431 Secondary Air Injection (AIR) System Pressure Sensor Performance diagnostic monitors the accuracy of the sensor signal. The 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 AIR 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 powertrain control module (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 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
    • 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 PCM 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.

  1. The Diagnostic System Check - Vehicle 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.

    2.

  2. 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.

    3.

  3. 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.

    4.

  4. This step determines if there is trapped pressure at the AIR pressure sensor.

    5.

  5. 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.

    6.

  6. This step checks for high electrical resistance in the AIR pressure sensor input circuit.

    7.

  7. 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

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn ON the ignition, with the engine OFF.
  2. Listen for secondary air injection (AIR) pump operation.

Is the AIR pump ON?

--

Go to DTC P2444

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Backprobe the input circuit of the AIR pressure sensor with a DMM to ground.

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
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the input circuit voltage of the AIR pressure sensor while operating the AIR pump.
  3. Command the AIR solenoid and pump ON with the scan tool. Refer to Scan Tool Output Controls .

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

5

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
  1. Inspect the following conditions:
    2. • A disconnected or restricted vacuum hose to the AIR pressure sensor
    • A loose or restricted air hose from the AIR pump to the AIR shut-off valve
  2. Repair as necessary.

Did you find and correct a condition?

--

Go to Step 15

Go to Step 8

8

  1. Connect a test lamp to the reference voltage circuit and ground.
  2. Turn ON the ignition, with the engine OFF.

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

10

  1. Test the input circuit of the AIR pressure sensor for high resistance. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 13

Go to Step 14

11

  1. Test for high resistance in the ground circuit of the AIR pressure sensor between the sensor and the splice in the sensor ground circuit. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Test for a poor electrical connection at the pressure sensor.
  3. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

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 powertrain control module (PCM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 15

--

15
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC.

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?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK