P0418 - SECONDARY AIR INJECTION SYSTEM RELAY A MALFUNCTION

The Secondary Air Injection System (SAI) is composed of an air pump that is driven by a belt or electric pump. This system also includes pressure sensors and check and switching valves. All of them are controlled by the PCM (Powertrain Control Module).

For the system pressure control, the PCM relies on input signals from one or more of the pressure sensors, which report that value. If the system pressure drops below the level established by the manufacturer, the pump will be activated. Then, it will open the appropriate valves to allow compressed ambient air to be pumped into the exhaust manifold.

The Diagnostic code P0418 OBDII is set when the PCM detects a malfunction of the secondary air injection pump relay “A” circuit, which is interpreted as a fault in the UPS System.

• The Check Engine light turns on.
• Difficulty in acceleration.
• Abnormal UPS system pump noises.

Reasons for storing the P0418 OBD2 fault code:

• Circuit wiring or connectors may not be tightened properly or may be damaged.
• The pump relay may be faulty.
• A fuse in the UPS system may be blown.
• It is possible that the pump is in bad condition or damaged.

To troubleshoot the DTC P0418 OBDII, try this:

• Initiate a diagnosis by consulting the Technical Service Bulletins (TBS).
• Perform an inspection of the Secondary Air Injection System components, and rule out any burn spots or wear on the secondary air injection system wires or connectors. Make repairs or replacements if necessary.
• Verify that the one-way check valves are working properly. If after such checks you determine they are inconsistent, fix or replace them.
• Perform an inspection of the system hoses, and make sure they are not in bad condition. Repair if necessary.
• Use a DVOM to perform resistance and continuity tests on the system circuit. The results should be compared to the manufacturer's specifications.
• If the resistance values do not match, make repairs.

• Check the pump for blockages or obstructions that may prevent it from working properly. Similarly, take into account the recommendations of the service manual to check the good condition of it. If it does not meet the requirements, replace it.