Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0418: Air Pump Relay Control Circuit: Description
The secondary Air Injection (AIR) pump relay controls the high current flow to the AIR pump. This allows the Powertrain Control Module (PCM) driver to control only the low current that is used by the relay coil. Ignition 1 voltage is directly supplied to the AIR pump relay coil. The PCM controls the relay by supplying a ground to the control circuit of the AIR pump relay. When the PCM commands the relay ON, the voltage of the control circuit should be low, near 0 volts. When the PCM commands the relay OFF, the voltage potential of the circuit should be high, near the battery voltage. If the PCM monitor detects a voltage other than expected, DTC P0418 sets.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.