DTC P0418: Secondary Air Injection Pump Relay Control Circuit: Description
WARNING: This page is about a different car, the 2002 Pontiac Aztek and 2002 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.
Ignition voltage is supplied directly to the relay. The control module supplies the ground path to the relay control circuit via an internal solid state device called a driver. Each driver has a fault line which is monitored by the control module. When the control module commands the relay ON, the voltage on the control circuit should be low, near 0 volts. When the control module commands the relay OFF, the voltage on the control circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, this Diagnostic Trouble Code (DTC) will set. The control module will monitor the control circuit for the following items:
- A short to ground.
- A short to voltage.
- An open circuit.
- An open relay.
- An internally shorted or excessively low resistance relay.