Results of Incorrect Operation

The PCM detects a system airflow problem by monitoring the heated oxygen senors (HO2S) and Short Term Fuel Trim (FT) values during normal Open Loop system operation. This is a passive test. If the passive test indicates a pass, the PCM takes no further action. If the passive test fails or is inconclusive, the PCM diagnostic will proceed with an intrusive or active test. The PCM will command the AIR system ON, during normal Closed Loop operation and under normal operating conditions. This is an active test. The active test will pass or fail based on the response from the HO2S. A drop in the HO2S response indicates that the AIR system is functioning normally. An increasing Short Term FT value also indicates a normally functioning system. The AIR diagnostic consists of the combination of the passive and active test. It requires failure of the passive and active tests on two consecutive key cycles to illuminate the malfunction indicator lamp (MIL) and store a DTC. If the PCM detects that the HO2S and Short Term FT did not respond as expected on both of the engine banks DTC P0410 sets. If the PCM detects that the HO2S and Short Term FT did not respond as expected on only one of the engine banks DTC P0491 for bank 1 or P0492 for bank 2 sets.

If incorrect voltage is present on the AIR solenoid or the AIR pump relay control circuits the device will not operate. This condition can be detected by the PCM, DTC P0412 for the AIR solenoid or P0418 for the AIR pump relay sets.

The following DTCs can set if a secondary air injection fault is detected:

• P0410- A system flow problem has been detected.
• P0412- A secondary AIR injection solenoid control circuit problem has been detected.
• P0418- A secondary AIR pump relay control circuit problem has been detected.
• P0491-A Bank 1 airflow problem has been detected.
• P0492-A Bank 2 airflow problem has been detected.