P0418 Secondary Air Injection System Relay 'A" Circuit Malfunction.
The DTC P0418 is detected the the AIR vacuum control solenoid circuit not operating as desired by the PCM.
An air pump is used on the vehicle to lower tail pipe emissions on
start-up. The Powertrain Control Module PCM grounds the Air pump relay
control circuit which energizes the Air pump. The PCM also grounds the
Air combination valve vacuum control solenoid circuit, which energizes
the Air vacuum control solenoid. Vacuum is then applied to both Air
combination valve diaphragms which opens the shut off valves. The PCM
enables both circuits simultaneously when Air system operations id
desired. When the AIR system is active, then Air pump forces fresh air
into the exhaust stream in order to accelerate catalyst operation. The
AIR combination valves replace the conventional check valves. When the
AIR system is inactive the shut off valves prevent air flow in either
direction.
Symptoms:
- Engine Light ON (or Service Engine Soon Warning Light)
- Engine hesitation
Possible Causes:
- Air Pump inoperative.
- Air bypass solenoid circuit open or shorted.
- Faulty AIR byspass solenoid circuit
Possible Solution:
- Visually inspect AIR pump harness and connector. Repair if necessary.
- Visually inspect AIR bypass valve harness and connector. Repair if necessary.
- Replaced AIR bypass valve
- Replaced Air pump
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