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?33?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?0 s 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 valve are in turn energized. The pump turns ON and the valve opens.
The secondary air injection pump sends pressurized filtered fresh air into the pipe/hose, through the open valve and into the exhaust manifold. 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 valve is 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 valve is closed to prevent air/exhaust flow in either direction.
The ECM monitors the secondary air injection system pressure by tracking voltage signal from the pressure sensor, which is integral to the solenoid (shutoff and check) valve assembly.
The ECM utilizes a 3 phase diagnostic routine to test the secondary air injection system:
During phase 1, DTCs P0411 and P2430 run and both the secondary air injection pump and the solenoid (shutoff and check) valve are activated. Normal secondary air function occurs. Expected system pressure is 5?3 kPa (0.7?.9 psi) above BARO.
During phase 2, DTCs P2430 and P2440 run and only the secondary air injection pump is activated. The valve is closed. Pressure sensor performance and valve deactivation are tested. Expected system pressure is 14?5 kPa (2.0?.6 psi) above BARO.
During phase 3, DTC P2444 runs and neither the secondary air injection pump nor the valve are activated. Secondary air injection pump deactivation is tested. Expected system pressure equals BARO.
The secondary air injection system includes the following components:
Note:
The secondary air injection solenoid valve and the pressure sensor are serviced as an assembly.
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 expected values, a DTC will set. Diagnostics detect the following conditions:
The following DTCs set when a secondary air injection system fault is detected:
Vehicle Identification Number (VIN)
This legal identifier is in the front corner of the instrument panel, on the
left side of the vehicle. It can be seen through the windshield from outside. The
VIN also appears on the Vehicle Certification and Service Parts labels and certificates
of title and registration.
Engine Identifi ...
Electrical Center Identification Views
Figure 1:
X70A Relay Block - Underhood Label (LUV)
Figure 2:
X70A Relay Block - Underhood, Top View (LUV)
Figure 3:
X50A Fuse Block - Underhood Label (LUV)
Figure 4:
X50A Fuse Block - Underhood Label (LUW)
...
Cooling System Description and Operation
Cooling System
The cooling system maintains the engine operating temperature at the efficient
level under any speed and operating condition. When the engine is cold, the
cooling system cools the engine slowly or not at all. The slow cooling of the
engine allows the engine to warm u ...