DTC P0412: Secondary Air Injection Relay Control Circuit: Description

The Secondary Air Injection (AIR) vacuum control solenoid is used as a switch to direct and control engine vacuum to the AIR shut-off valve. Voltage is supplied to the AIR solenoid by the ignition 1 voltage circuit. The Powertrain Control Module (PCM) commands the AIR solenoid on by supplying a ground on the control circuit by an internal switch called a driver. This action completes the circuit and energizes the AIR solenoid allowing vacuum to open the shut-off valve. The PCM driver monitors the control circuit voltage constantly for proper voltage conditions. When the PCM commands the AIR solenoid on, the circuit voltage should be low, near zero volts. When the PCM commands the control circuit off, the voltage potential of the circuit should be high, near the battery voltage. If the PCM detects a voltage other than what is expected, DTC P0412 sets.