Secondary Air Injection System Monitor (Electric Air Pump System)

The Secondary Air Injection (AIR) system monitor is an on-board strategy designed to monitor the proper function of the secondary air system. The AIR monitor for the Electric Air Pump system consists of two monitor circuits: an AIR circuit to diagnose problems with the primary circuit side of the Solid State Relay (SSR), and an AIR monitor circuit to diagnose problems with the secondary circuit side of the Solid State Relay. A functional check is also performed that tests the ability of the AIR system to inject air into the exhaust. The functional check relies upon H02S sensor feedback to determine the presence of air flow. The monitor is enabled during AIR system operation and only after certain base engine conditions are first satisfied. Input is required from the ECT, IAT and CKP sensor, and the H02S monitor test must also have passed without a fault detection to enable the AIR monitor. The AIR monitor is also activated during on demand self-test. The following examples are probable conditions:

1. The AIR circuit is normally held high through the SAIR Bypass solenoid and Solid State Relay when the output driver is off. Therefore a low AIR circuit indicates a driver is always on and a high circuit indicates an open in the PCM. The DTC associated with this test is DTC P0412. See Fig 1.
2. The AIR monitor circuit is held low by the resistance path through the Air Pump when the pump is off. If the AIR monitor circuit is high there is either an open circuit to the PCM from the pump or there is power supplied to the Air Pump. If the AIR monitor is low when the pump is commanded on, there is either an open circuit from the SSR or the SSR has failed to supply power to the pump. The DTCs associated with this test are DTCs P1413 and P1414.
3. The functional check may be done in two parts; at startup when the Air Pump is normally commanded on, or during a hot idle if the startup test was not able to be performed. The flow test relies upon the H02S sensor to detect the presence of additional air in the exhaust when introduced by the Secondary Air Injection system. The DTC associated with this test is DTC P0411.
4. The Malfunction Indicator Light (MIL) is illuminated after one of the above tests fails on 2 consecutive drive cycles.

Fig 1: Identifying Secondary Air Injection System Monitor Components (Electric Air Pump)

Courtesy of FORD MOTOR CO.