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 , and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

DTCs P0412 and P0418 are Type B DTCs.

DTCs P0412 and P0418 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

Description and Operation Reference

Secondary Air Injection System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, command the affected relay ON and OFF with a scan tool. Feel or listen to verify that the affected relay turns ON and OFF with each command.
2. Engine running, observe the DTC information with a scan tool. DTCs P0412 or P0418 should not set.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

1. Ignition OFF, disconnect the affected relay.
2. Ignition ON, connect a test lamp between the positive terminal at the battery and the relay control circuit terminal.
3. Command the relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the ECM.

⇒	If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

4. Connect an appropriately fused jumper wire between the positive voltage terminal at the battery and the load voltage supply circuit terminal and verify load activation.

⇒	If the load does not activate, test the load voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the load.

5. Ignition ON, connect an appropriately fused jumper wire between the relay switch voltage supply circuit terminal and the load voltage supply circuit terminal and verify load activation.

⇒	If the load does not activate, test the relay switch voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its fuse is open, test all components connected to the fuse and replace as necessary.

6. Ignition ON, verify that a test lamp illuminates between the relay coil voltage supply circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the relay coil voltage supply circuit for a short to ground or an open/high resistance.

7. If all circuits and the ECM test normal, test or replace the affected relay.

Relay Test

1. Test between the normally-closed switch terminals, if any, for 0 ohms.
2. Test between the normally-open switch terminals for infinite ohms.
3. Test between each switch terminal and either coil terminal for infinite ohms.
4. Connect the relay coil terminals to ground and fused power to energize the relay.
5. Test between the normally-closed switch terminals, if any, for infinite ohms.
6. Test between the normally-open switch terminals for 0 ohms.
7. Test between each switch terminal and either coil terminal for 0 volts.

Ignition ON, command the relay ON and OFF with a scan tool. Feel or listen to verify that the relay turns ON and OFF with each command.