DTC P0412: Secondary Air Injection Pump Relay Control Circuit: Description

Ignition voltage is supplied directly to secondary Air Injection (AIR) relay. The PCM supplies ground path to relay control circuit via an internal solid state device called a driver. Each driver has a fault line which is monitored by the PCM. When PCM commands the solenoid on, voltage on control circuit should be low, about zero volts. When PCM commands the solenoid off, voltage on the control circuit should be high, about battery voltage. If the fault detection circuit senses a voltage other than what is expected, this DTC will set.

The PCM will monitor the control circuit for short to ground, short to voltage, open circuit, open solenoid or an internally-shorted or excessively low resistance solenoid.