Secondary Air Injection System Description
The Secondary Air Injection System aids in the reduction of hydrocarbon exhaust emissions during a cold start. This occurs when the start-up engine coolant temperature (ECT) is between -10 to +56°C (14-133°F), the intake air temperature (IAT) is greater than -10°C (14°F) and it has been more than 60 minutes since the last engine start. The secondary air injection pump operates 5-60s after start-up.
The engine control module (ECM) activates the secondary air injection system by simultaneously completing the ground paths for the secondary air injection pump relay and the secondary air injection solenoid (shutoff and check) valve relay. This action closes the relays' internal contacts. The pump and both valves are in turn energized. The pump turns ON and both valves open.
The secondary air injection pump sends pressurized filtered fresh air into the pipes/hoses, through the open valves and into the exhaust manifold(s). The extra air accelerates the catalyst operation, helping it to reach operating temperature faster. The secondary air injection pump remains ON for a short period of time after the valves are commanded OFF. When the pump is commanded OFF it will not run or be activated until the next vehicle cold start. When the secondary air injection system is inactive, the valves are closed to prevent air/exhaust flow in either direction.
The ECM monitors the secondary air injection system pressure by tracking voltage signals from the pressure sensors, which are integral to the solenoid (shutoff and check) valve assemblies.
The ECM utilizes a 3 phase diagnostic routine to test the secondary air injection system:
During phase 1, DTCs P0411, P2430 and P2435 run and both the secondary air injection pump and the solenoid (shutoff and check) valves are activated. Normal secondary air function occurs. Expected system pressure is 10-15kPa (1.5-2.2psi) above BARO.
During phase 2, DTCs P2430, P2435 and P2440 run and only the secondary air injection pump is activated. The valves are closed. Pressure sensor performance and valve deactivation are tested. Expected system pressure is 20-30kPa (2.9-4.4psi) above BARO.
During phase 3, DTC P2444 runs and neither the secondary air injection pump nor the valves are activated. Secondary air injection pump deactivation is tested. Expected system pressure equals BARO.
The secondary air injection system includes the following components:
- The secondary air injection pump-The electric secondary air injection pump supplies pressurized, filtered air to the secondary air injection solenoid (shutoff and check) valves. The secondary air injection pump is a turbine type pump that is permanently lubricated and requires no periodic maintenance.
- The secondary air injection solenoid (shutoff and check) valve assemblies-The valve assemblies have direct current (DC) motor operated valves. When the valve motors are energized by the secondary air injection solenoid valve relay, the valves open, pressurized air from the secondary air injection pump flows through the valves and is directed into the exhaust manifold(s).
- The secondary air injection pressure sensors-The pressure sensors are integral to the secondary air injection solenoid valve assemblies. The sensors are 3-wire sensors that measure the secondary air injection system pressure at the inlets of the valve assemblies.
- The secondary air injection pump relay-The relay supplies high current and battery voltage to the secondary air injection pump. The ECM commands the relay ON by supplying a ground to the relay control circuit.
- The secondary air injection solenoid valve relay-The relay supplies high current and battery voltage to the secondary air injection solenoid valves. The ECM commands the relay ON by supplying a ground to the relay control circuit.
- The pipes and hoses-The secondary air injection pump inlet hose carries filtered air from the engine intake air cleaner to the secondary air injection pump inlet. The secondary air injection pump pipe carries the air from the pump outlet to the solenoid valves which in turn feed the exhaust manifold(s).
The secondary air injection solenoid valve and the pressure sensor are serviced as an assembly.
The secondary air injection solenoid valve relay is soldered directly to a printed circuit board (PCB) within the fuse block and is not serviceable as a separate component.