The secondary air injection (AIR) system reduces exhaust emissions following
initial engine start-up. This occurs when the engine start-up coolant temperature
is between 5-80°C (41-176°F), and the intake air temperature (IAT)
is more than 5°C (41°F). The AIR pump will operate until Closed Loop operation
is achieved.
The powertrain control module (PCM) activates the AIR system by simultaneously
suppling a ground to the AIR pump relay and the AIR solenoid relay. This action closes
the internal contacts of the AIR pump relay, energizing the AIR pump, and also closes
the internal contacts of the AIR solenoid relay, energizing the AIR solenoid, opening
the shut-off valve. The AIR pump forces pressurized fresh air into the pipes/hoses
and past the shut-off valve into the bank 1 exhaust manifold, accelerating
the catalyst operation. When the AIR system is inactive, the AIR shut-off valve prevents
airflow in either direction.
The AIR system includes the following components:
| • | The AIR Pump--The AIR pump supplies pressurized, filtered air to
the exhaust stream. The AIR pump is a turbine type pump which is permanently lubricated
and requires no periodic maintenance. The AIR pump for the 4.6L engine will draw a
steady 45-50 amps under normal operation. |
| | Important: An audible exhaust noise may be heard at
the inlet of the shut-off valve, when the shut-off valve is opened and the AIR crossover
hose is removed from the shut-off valve.
|
| • | The AIR Shut-Off Valve--The AIR shut-off valve has an electronic solenoid
mounted on the valve. The resistance of the solenoid is 4-6 ohms and
the current draw is 2-3 amps. The solenoid opens the shut-off valve when
battery voltage is applied to the valve. Once opened, pressurized air from the AIR
pump flows past the shut-off valve and is directed into the bank 1 exhaust
manifold through an outlet pipe. The shut-off valve contains an internal check valve
that prevents fresh air from being drawn into the exhaust manifold by providing a
positive seal when the AIR system is inactive. The solenoid, valve, and outlet pipe
are serviced as an assembly. |
| • | The AIR Pump Relay--The AIR pump relay supplies high current and
battery voltage to the AIR pump. The resistance of the AIR pump relay coil is 65-75 ohms. |
| • | The AIR Solenoid Relay--The AIR solenoid relay supplies high current
and battery voltage to the AIR solenoid that is an integral part of the shut-off valve.
The PCM commands the AIR solenoid relay ON by suppling a ground on the control circuit
of the relay. The resistance of the AIR solenoid relay coil is 75-85 ohms. |
| • | Pipes and Hoses--The pipes/hoses carry the air from the AIR pump
past the AIR check valve and into the exhaust manifold. A pipe connects the check
valve to the exhaust manifold. The AIR system also utilizes a hose to carry the filtered
air to the inlet of the AIR pump. |
| • | The Inlet Filter--There are 2 types of inlet filters. The
first type utilizes the air filter for the engine. This system draws filtered air
directly from the air cleaner assembly. The second type uses a separate filter that
provides filtered air exclusively for the AIR system. |
Results of Incorrect Operation
The powertrain control module (PCM) can detect a secondary air injection (AIR)
system airflow fault by monitoring the heated oxygen sensor (HO2S) bank 1 sensor 1
during normal engine operation. This is an active test. The PCM will command the AIR
system ON during Closed Loop operation to perform this test. The active test will
pass or fail based on the response from the HO2S 1. The active test consists
of three tests run at 3 second intervals. A decreasing HO2S voltage parameter
response indicates that the secondary AIR system is functioning properly. If the PCM
does not detect a decreasing response from the HO2S 1, DTC P0410 will
set.
The following DTCs can set if an AIR injection fault is detected:
| • | DTC P0410--A system airflow condition has been detected. |
| • | DTC P0412--An AIR solenoid relay coil circuit fault has been
detected. |
| • | DTC P0418--An AIR pump relay coil circuit fault has been detected. |
