Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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. The secondary AIR injection pump, provides filtered air on demand to the AIR check valve assembly. The AIR check valve assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR CNTRL relay supplies the current needed to operate the AIR solenoid that is integral to the check valve assembly. A pressure sensor, also integral to the check valve assembly, is used to monitor the air flow from the AIR pump. The control module supplies the internal pressure sensor with a 5-volt reference, an electrical ground, and a signal circuit. The signal circuit provides the control module with a voltage relative to internal AIR pressure changes.

The AIR diagnostic uses 3 phases to test the AIR system:

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The control module can detect faults in the AIR pump, AIR solenoid, pressure sensor, related wiring, and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing. Refer to Secondary Air Injection System Description for further information.

The pressure sensor signal is less than 0.25 volt for at least 12.5 seconds.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. If DTCs P0641 or P0651 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Engine running, observe that the AIR Pressure Sensor parameter approximately equals BARO.

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 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 ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 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 ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.

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 ECM.

5. Install a 3-amp fused jumper wire between the signal circuit terminal and the 5-volt reference circuit terminal. 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 a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

6. If all circuits and the ECM test normal, test or replace the AIR solenoid valve.

Measure the AIR solenoid for a resistance of 4.8-6.8  ohms across the voltage supply terminal and the ground terminal at the AIR check valve at an ambient temperature of approximately 20°C (68°F).

Solenoid Valve

Apply appropriately 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.

Engine running, enable the AIR pump relay with a scan tool and observe that the AIR Pressure Sensor parameter equals approximately 10-20 kPa above BARO.