OBD-II code P0418 indicates a malfunction in the electrical control circuit for the secondary air injection system. This system pumps fresh air into the exhaust to reduce emissions during cold starts. The code sets when the PCM detects an open, short, or other circuit fault in the air pump relay, solenoid, or associated wiring.
The relay that controls the secondary air injection pump may be stuck open or closed, or its coil may be damaged, preventing proper circuit operation.
Corrosion, broken wires, or loose connections in the air pump control circuit can cause high resistance or open circuits.
A short circuit or excessive current draw can blow the fuse protecting the air pump circuit, cutting power to the pump or relay.
The pump motor may be seized, shorted internally, or drawing excessive current, causing circuit faults.
The solenoid or vacuum-operated valve that directs air into the exhaust can fail electrically, causing a circuit fault.
The powertrain control module may have an internal driver fault, but this is the least likely cause and should only be considered after all other possibilities are ruled out.
Yes, in most cases the vehicle is safe to drive. The secondary air system only operates during cold starts to reduce emissions, so drivability is usually unaffected. However, you may fail an emissions inspection.
No, PCM failure is very rare for this code. The most common causes are a faulty air pump relay, wiring issues, or a blown fuse. Replacing the PCM should only be considered after all other components and circuits have been thoroughly tested and ruled out.
It is an emissions system that injects fresh air into the exhaust manifold or catalytic converter during cold starts. This helps burn unburned fuel, reducing hydrocarbon emissions and warming up the catalytic converter faster.
The code may clear if the fault is intermittent, but it will return if the underlying problem persists. The PCM runs the air system monitor only under specific conditions, so the code may not set immediately after a repair.