P2431

P2431-SECONDARY AIR INJECTION SYSTEM AIR FLOW SENSOR CIRCUIT PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

For 20 seconds following a vehicle cold start, the air injection system delivers a controlled amount of outside air into the exhaust system, upstream of the catalytic converters, in order to help reduce hydrocarbon and carbon monoxide gas emissions.

- When Monitored:
Engine Coolant Temperature (ECT) above 0° C (32° F), ambient air temperature within approximately two degrees of ECT, actual air flow is less than or equal to model airflow, and Secondary Air Flow diagnostic counter above 100 (approximately three seconds). Secondary Air Pump Control circuit active.

- Set Condition:
The Powertrain Control Module (PCM) detects that the measured air flow is below a calculated minimum value, above a calculated maximum value, or there is no difference between the minimum measured air flow value and the maximum measured air flow value during monitoring.

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. DTC IS ACTIVE

WARNING: The normal operating temperature of the exhaust system is very high. Never work around or attempt to service any part of the exhaust system until it has cooled. Special care should be taken when working near any part of the exhaust system. The temperature rises to a high level after a short period of engine operating time.

NOTE: Diagnose and repair any system voltage DTCs before continuing with this test.

1. Turn the ignition on.
2. With the scan tool, select View DTCs and review the DTC environmental data for this DTC.

Is the good trip counter greater than 0?

Yes

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

No

- Go To 2

2. FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN OR HIGH RESISTANCE

1. Turn the ignition off.
2. Disconnect the C1 Secondary Air Pump Assembly harness connector.
3. Turn the ignition on.
4. Using a 12-volt test light connected to ground, check the Fused Ignition Switch Output circuit in the C1 Secondary Air Pump Assembly harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Go To 3

No

- Repair the Fused Ignition Switch Output circuit for an open circuit or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

3. (K157) MAF SENSOR SIGNAL CIRCUIT VOLTAGE

1. Turn the ignition on.
2. Measure the voltage of the (K157) MAF Signal circuit in the C1 Secondary Air Pump Assembly harness connector.

Is the voltage between 4.8 and 5.1 volts?

Yes

- Go To 4

No

- Go To 6

4. (K957) MAF SENSOR GROUND CIRCUIT TEST

1. Turn the ignition off.
2. Using a 12-volt test light connected to 12 volts, check the (K957) MAF Sensor Ground circuit in the C1 Secondary Air Pump Assembly harness connector.

NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.

Is the test light illuminated and bright?

Yes

- Go To 5

No

- Go To 9

5. SECONDARY AIR PUMP ASSEMBLY
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Secondary Air Pump Assembly and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Secondary Air Pump Assembly.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. (K157) MAF SENSOR SIGNAL CIRCUIT SHORTED TO VOLTAGE

1. Turn the ignition off.
2. Disconnect the Powertrain Control Module (PCM) C2 harness connector.
3. Turn the ignition on.
4. Measure the voltage of the (K157) MAF Sensor Signal circuit in the C1 Secondary Air Pump Assembly harness connector.

Is there any voltage present?

Yes

- Repair the (K157) MAF Sensor Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 7

7. (K157) MAF SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

1. Turn the ignition off.
2. Measure the resistance between ground and the (K157) MAF Sensor Signal circuit in the C1 Secondary Air Pump Assembly harness connector.

Is the resistance above 100 Ohms?

Yes

- Go To 8

No

- Repair the (K157) MAF Sensor Signal circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. (K157) MAF SENSOR SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

NOTE: When checking circuits at the Powertrain Control Module (PCM), be careful not to damage or distort the connector terminals. Improper measurement technique could result in poor pin to terminal contact.

1. Measure the resistance of the (K957) MAF Sensor Ground circuit between the C1 Secondary Air Pump Assembly harness connector and the PCM.

Is the resistance below 5.0 Ohms?

Yes

- Go To 10

No

- Repair the (K957) MAF Sensor Ground for an open circuit or high resistance.
- Perform the PCM VERIFICATION TEST. Powertrain Verification Test.

10. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Secondary Air Pump Assembly and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related connectors.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module (PCM). Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.