Air Injection: Testing and Inspection

Secondary Air Injection System Check:

Secondary Air Pump Circuit.:

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. For air flow from electric switching valve
4. 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.

Circuit Description
During cold starts, above -8°C (17°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.

Test Description
Numbers refer to circled numbers on the diagnostic chart.

1. The PCM should energize the air pump when engine coolant temperature is greater than -8°C (17°F) and fuel system not in "Closed Loop". If any diagnostic trouble codes (DTC) are present the PCM will not energize the air pump.
2. The PCM should de-energize the air pump relay when engine speed exceeds 2825 rpm.
3. Air pump relay is located in the underhood electrical center.
4. Selecting "Miscellaneous Test" then outputs and the AIR system on the Tech 1 (or equivalent Scan tool) with the ignition "ON" and the engine not running should enable the air pump and integral stop valve.

Diagnostic Aids
There is a possibility that the air pump motor will be operating, but no air is being distributed to the air system. The integral stop valve may not be opening or a restriction in the air hoses or pipes may be the cause.