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Chevrolet Equinox Service Manual: Secondary Air Injection System Description Engine Control

Chevrolet Equinox Service Manual / Powertrain / Internal Combustion Powertrain Control / Secondary Air Injection System Description Engine Control

The Secondary Air Injection System aids in the reduction of hydrocarbon exhaust emissionsduring 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. Thesecondary air injection pump operates 5–60-s after start-up.

The engine control module (ECM) activates the secondary air injection system by simultaneouslycompleting the ground paths for the secondary air injection pump relay and the secondaryair 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 turnsON 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 acceleratesthe catalyst operation, helping it to reach operating temperature faster. The secondaryair injection pump remains ON for a short period of time after the valves are commandedOFF. When the pump is commanded OFF it will not run or be activated until the nextvehiclecold start. When the secondary air injection system is inactive, the valves are closedto prevent air/exhaust flow in either direction.

The ECM monitors the secondary air injection system pressure by tracking voltage signalsfrom 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 injectionsystem:

During phase-1, DTCs P0411, P2430 and P2435 run and both the secondary air injectionpump and the solenoid (shutoff and check) valves are activated. Normal secondary airfunction occurs. Expected system pressure is 5–13-kPa-(0.7–1.9-psi) above BARO.

During phase-2, DTCs P2430, P2435 and P2440 run and only the secondary air injectionpump is activated. The valves are closed. Pressure sensor performance and valve deactivationare tested. Expected system pressure is 14–25-kPa-(2.0–3.6-psi) above BARO.

During phase-3, DTC P2444 runs and neither the secondary air injection pump nor thevalves are activated. Secondary air injection pump deactivation is tested. Expectedsystem pressure equals BARO.

The secondary air injection system includes the following components:

The secondary air injection pump—The electric secondary air injection pump suppliespressurized, filtered air to the secondary air injection solenoid (shutoff and check)valves. The secondary air injection pump is a turbine type pump that is permanentlylubricated and requires no periodic maintenance.

Note:The secondary air injection solenoid valve and the pressure sensor are serviced asan assembly.

The secondary air injection solenoid (shutoff and check) valve assemblies—The valveassemblies have direct current (DC) motor operated valves. When the valve motors areenergized by the secondary air injection solenoid valve relay, the valves open, pressurizedair from the secondary air injection pump flows through the valves and is directedinto the exhaust manifold(s).The secondary air injection pressure sensors—The pressure sensors are integral tothe secondary air injection solenoid valve assemblies. The sensors are 3-wire sensorsthat measure the secondary air injection system pressure at the inlets of the valveassemblies.The secondary air injection pump relay—The relay supplies high current and batteryvoltage to the secondary air injection pump. The ECM commands the relay ON by supplyinga ground to the relay control circuit.The secondary air injection solenoid valve relay—The relay supplies high current andbattery voltage to the secondary air injection solenoid valves. The ECM commands therelay ON by supplying a ground to the relay control circuit.The pipes and hoses—The secondary air injection pump inlet hose carries filtered airfrom the engine intake air cleaner to the secondary air injection pump inlet. Thesecondary air injection pump pipe carries the air from the pump outlet to the solenoidvalves which in turn feed the exhaust manifold(s).System Fault Detection

The ECM monitors the secondary air injection system for faults during cold start operation.When the system's pressure or relay circuits operations vary too far from the expectedvalues, a DTC will set. Diagnostics detect the following conditions:

A partially or fully blocked or leaking secondary air injection systemA malfunctioning secondary air injection pumpA malfunctioning secondary air injection solenoid (shutoff and check) valve assemblyA malfunctioning secondary air injection pressure sensorA restricted exhaust systemA malfunctioning secondary air injection pump and secondary air injection valve relay

The following DTCs set when a secondary air injection system fault is detected:

DTC-P0411 – A secondary air injection system insufficient airflow fault conditionhas been detected.DTC-P0412 – A secondary air injection valve relay coil circuit fault condition hasbeen detected.DTC-P0418 – A secondary air injection pump relay coil circuit fault condition hasbeen detected.DTC-P2430 – A secondary air injection pressure sensor signal stuck in range faultcondition has been detected – bank-1 (Left Hand).DTC-P2431 – A skewed air injection pressure sensor signal has been detected – bank-1(Left Hand).DTC-P2432 – A secondary air injection pressure sensor signal voltage below the minimumrange of the sensor fault condition has been detected – bank-1 (Left Hand).DTC-P2433 – A secondary air injection pressure sensor signal voltage is above themaximum range of the sensor fault condition has been detected – bank-1 (Left Hand).DTC-P2435 – A secondary air injection pressure sensor signal stuck in range faultcondition has been detected – bank-2 (Right Hand).DTC-P2436 – A skewed air injection pressure sensor signal has been detected – bank-2(Right Hand).DTC-P2437 – A secondary air injection pressure sensor signal voltage below the minimumrange of the sensor fault condition has been detected – bank-2 (Right Hand).DTC-P2438 – A secondary air injection pressure sensor signal voltage is above themaximum range of the sensor fault condition has been detected – bank-2 (Right Hand).DTC-P2440 – One or both of the solenoid (shutoff and check) valves are stuck openor a system leak between the pump and the valves has been detected.DTC-P2444 – A secondary air injection pump stuck ON fault condition has been detected.
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