P0418 CHEVROLET - Secondary Air Injection Pump Relay Control Circuit
When is the code detected?If the fault detection circuit senses a voltage other than what the Powertrain Control Module (PCM) is expects, the fault line status changes causing the code P0418 to set.
P0418 Chevrolet DescriptionThe Powertrain Control Module (PCM) controls the relay by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. Each driver has a fault line which the PCM monitors. When the PCM commands a component ON, the voltage of the control circuit should be low (near 0 volts). When the PCM commands the control circuit to a component OFF, the voltage potential of the circuit should be high (near the battery voltage).
The relay controls the high current flow to the AIR injection pump integral bypass valve. This allows the PCM driver to only have to control the relatively low current used by the relay.