P0412: Secondary Air Injection Solenoid Relay Control Circuit: Description
WARNING: This page is about a different car, the 2002 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.
The Powertrain Control Module (PCM) commands the AIR control solenoid ON by grounding the control circuit though an internal switch called a driver. Voltage is supplied to the control solenoid though the ignition 1 voltage circuits and protected by a fuse. When the PCM commands the solenoid ON, the voltage of the control circuit should be low or near 0 volts. When the PCM commands the solenoid OFF, the voltage potential of the circuit should be high, near battery voltage. If the PCM detects a voltage other than what is expected, this DTC will set.