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 and the ESV solenoid 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 and ESV are 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.
Air Management Test:
AIR Control System Circuit Diagram:
Circuit Description
An electric air control valve solenoid directs air into the exhaust ports or away from the exhaust ports. During cold starts, above 15°C (59°F), the ECM completes the ground circuit and the ESV solenoid and electric air pump are energized.
Air is directed to the exhaust ports whenever the engine is started. When the fuel system goes to "Closed Loop," the ECM opens the ground circuit.
When the ESV solenoid and electric air pump are de-energized, air is directed away from the exhaust ports until the electric air pump stops spinning.
Air Management Check:
Test Description
Numbers refer to circled numbers on the diagnostic chart.
1. This is a system performance test. If both the electric air pump and ESV are functioning properly the amount of fresh air flowing passed the oxygen sensor will cause a false lean condition (low ox voltage). When the output test is enabled it will only be "ON" for 5 seconds.
2. Test for a grounded electric switching valve circuit. The ESV solenoid is normally closed and should hold vacuum.
3. Checks for voltage from battery through a fuse to the solenoid.
4. Checks for an open control circuit. Using the Tech 1 will energize the ESV solenoid if the ECM and circuits are normal. In this step, if the test light is "ON", circuits are normal and the valve is at fault.
Air Management Check:
Test Description
Numbers refer to circled numbers on the diagnostic chart.
1. Checks for an open control circuit. Grounding the ALDL will energize the solenoid, if the ECM and circuits are normal. In this step, if the light is "ON", circuits are normal and fault is in the relay.