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1. Based upon stored fault codes for secondary air system, there is little or no flow of secondary air into engine. Typical causes for this issue are failed secondary air pumps and/or secondary air check valves. Secondary air pump should operate under normal circumstances when vehicle is first started to perform system test. Pump will normally be heard running when standing in front right corner of vehicle. 2. The secondary air pump is located in the right front of engine compartment. A secondary air pump relay located in the glove box is controlled by the engine control module and sends power to the secondary air pump. 3. Air pump can be disconnected and supplied with power and ground at pump to verify operation is possible. 4. Check valve on front right of cylinder head can be supplied with vacuum and visually checked for opening of valve. 5. Vacuum line from check valve to operating solenoid should also be inspected for cracks or being disconnected. Vacuum line follows right side of cylinder head to back of cylinder head to the secondary air solenoid located under left rear side of intake manifold. 6. The solenoid should allow vacuum flow to the check valve during vacuum pump operation. The solenoid is controlled directly by the engine control module and receives power during key-on-engine-off. Potential Causes: A.I.R. Check Valve Engine Control Module (ECM) Codes — Engine control module fault. Defective Secondary Air Pump Secondary Air Pump Relay Secondary Air Supply Hose Broken Vacuum Line Diagnostic Codes: P0491, P0492 Author: Robert Jacobs Average Reported Mileage: 69066
