Air Injection: Testing and Inspection
Functional Check:Electric Air Pump
With engine at normal operating temperature in neutral at idle, connect a "Scan" tool. Select "Miscellaneous test" then "Output test". Select "AIR system" in "Output test" directory. Exit to "Data list" and select oxygen sensor voltages for both left and right oxygen sensors. Enable the "Output test" for the AIR system.
The "Output test" will energize the electric air pump for only 5 seconds. When the "Output test" is enabled, the oxygen sensor voltages for both sensors should remain under .4 volts because air is being directed to the exhaust ports.
If the oxygen sensor voltages remain low during the "Output test" the electric air pump is operating satisfactorily.
Inspect:
Electric Air Pump
1. For a seized electric air pump
2. Hoses, tubes and all connections for leaks and proper routing
3. AIR pump for proper mounting
Hoses and Pipes
1. Hose or pipe for deterioration or holes
2. All hoses or pipe connections, and clamp tightness
3. Hose or pipe routing
4. If a leak is suspected on the pressure side of the system or if a hose or pipe has been disconnected on the pressure side, the connections should be checked for with a soapy water solution. With the electric air pump running, bubbles will form if a leak exists.
Check Valve
1. Check valves should be inspected whenever the hose is disconnected or when failure is suspected.
2. Blow through the check valve toward the cylinder head, then suck back through the valve. Flow should only be in one direction. If flow is in both directions, replace check valve.
Air Management Test:
Air Injection System:
Circuit Description
During cold starts, above 12°C (55°F), the PCM completes the ground circuit to the air pump relay which enables the air pump and integral stop valve.
Air is directed to the exhaust ports whenever the engine is started. When the fuel system goes to "Closed Loop," the PCM opens the ground circuit.
When the electric air pump is de-energized, an integral stop valve closes to prevent air from flowing into the exhaust manifold.
Chart C-6 AIR System Check:
Test Description
Numbers refer to circled numbers on the diagnostic chart.
1. This is a system performance test. If both the AIR pump and AIR check valve are functioning properly, the amount of fresh air flowing past the O2S will cause a false lean condition (low voltage). Move quickly through these first two steps.
2. Checks the PCM's ability to shut "OFF" the AIR pump. Once turned "OFF", the AIR pump should stay "OFF" for at least 200 seconds.
3. Checks for battery voltage for the energizing coil and switching portions of the AIR pump relay.
4. Checks for an open control circuit. Grounding the diagnostic "Test" terminal or using the Tech 1 "Output Test" will energize the AIR pump relay if the PCM and circuits are normal.