Circuit Description
The Secondary Air Injection (AIR) System aids in the reduction of hydrocarbon exhaust emissions during a cold start-up. This occurs when the start-up engine coolant temperature (ECT) is between 5-50°C (41-122°F), and the intake air
temperature (IAT) is between 5-60°C (41-140°F). The AIR pump operates 5-60 seconds after start-up.
The engine control module (ECM) activates the AIR system by simultaneously supplying a ground to the AIR pump and the AIR CNTRL relays. This action closes the relays' internal contacts. The AIR pump and the AIR check valve assembly are in turn energized,
the pump runs and the check valve opens.
The AIR pump sends pressurized fresh air into the pipes/hoses through the check valve, and into the bank 2 exhaust manifold. The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The AIR pump remains
ON for a short period of time after the check valve is commanded OFF. When the AIR pump is commanded OFF, it will not run or be activated until the next vehicle start. When the AIR system is inactive, the closed AIR check valve prevents air/exhaust flow in either
direction.
The AIR system pressure sensor that integral to the check valve is used to monitor pressure at the AIR check valve assembly inlet, during the commanded ON/OFF states.
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:
| • | Phase 1--The ECM commands the AIR pump and check valve ON. The ECM monitors the AIR pressure sensor signal for an increase over BARO to a pre-determined threshold. This verifies a properly operating system. |
| • | Phase 2--The AIR pump remains commanded ON and the check valve is commanded OFF. The ECM monitors the AIR pressure sensor signal to increase further to pre-detremined threshold. This verifies that the check valve is not stuck open. |
| • | Phase 3--The AIR pump is commanded OFF. The ECM monitors the AIR pressure signal to return to BARO. This verifies the AIR pump is not stuck ON. |
| • | DTCs P0411 and P2430 run during Phase 1 |
| • | DTCs P2430 and P2440 run during Phase 2 |
| • | DTC P2444 runs during Phase 3 |
The AIR system includes the following components:
| • | The AIR pump--The electric AIR pump supplies pressurized, filtered air to the AIR check valve. The AIR pump is a turbine type pump that is permanently lubricated and requires no periodic maintenance. |
| | Important: The AIR solenoid, control/shut-off valve, and the pressure sensor are serviced as an assembly.
|
| • | The AIR solenoid--The AIR solenoids opens the AIR check valve when the solenoid is energized by the AIR CNTRL relay. |
| | Important: An audible exhaust or air fluttering noise may be heard at the control solenoid valve/pressure sensor assembly inlet when the valve is open and the AIR hose is removed from the control solenoid valve/pressure sensor assembly.
|
| • | The AIR check valve assembly--The AIR solenoid valve/pressure sensor assembly has a solenoid mounted valve. When the valve is open by the solenoid, pressurized air from the AIR pump flows through the control solenoid valve/pressure sensor assembly
and is directed into the bank 2 exhaust manifold through an outlet pipe. |
| • | The AIR pressure sensor--The AIR pressure sensor is a part of the AIR control solenoid valve/pressure sensor assembly. The sensor is a 3-wire sensor that measures the AIR system pressure at the AIR control solenoid valve/pressure sensor assembly
inlet. |
| • | The AIR pump relay--The AIR pump relay supplies high current and battery voltage to the AIR pump. The ECM commands the relay ON by supplying a ground to the relay control circuit. |
| • | The AIR CNTRL relay--The AIR CNTRL relay supplies high current and battery voltage to the AIR solenoid. The ECM commands the relay ON by supplying a ground to the relay control circuit. |
| • | The pipes and hoses--The AIR system hose carries filtered air from the engine air cleaner to the AIR pump inlet. The pipe/hoses carry the air from the AIR pump to the AIR check valve assembly and on to the exhaust manifold. |
| • | The inlet filter--The AIR system does not have a separate inlet air filter. Filtered air is drawn from the engine air cleaner assembly. |
Results of Incorrect Operation
The engine control module (ECM) monitors the Secondary air injection (AIR) System for faults during cold start-up operation. When the system's pressure or relay circuits operations vary too far from the predicted values, a DTC will set. Diagnostics detect
the following conditions:
| • | A partially blocked or leaking AIR system |
| • | A malfunctioning AIR pump |
| • | A malfunctioning AIR control solenoid valve/pressure sensor assembly |
| • | A malfunctioning AIR pressure sensor |
| • | A restricted exhaust system, forward of the catalytic converter |
| • | A malfunctioning AIR pump and AIR valve relay |
The following DTCs set when an AIR system fault is detected:
| • | DTC P0411--An AIR system insufficient airflow fault condition has been detected. |
| • | DTC P0412--An AIR valve relay coil circuit fault condition has been detected. |
| • | DTC P0418--An AIR pump relay coil circuit fault condition has been detected. |
| • | DTC P2430--An AIR pressure sensor stuck in range fault condition has been detected. |
| • | DTC P2431--An AIR pressure sensor range/performance fault condition has been detected. |
| • | DTC P2432--An AIR pressure sensor signal voltage below the minimum range of the sensor fault condition has been detected. |
| • | DTC P2433--An AIR pressure sensor signal voltage is above the maximum range of the sensor fault condition has been detected. |
| • | DTC P2440--An AIR check valve stuck open or airflow leak fault condition has been detected. |
| • | DTC P2444--An AIR pump stuck ON fault condition has been detected. |
