Your Vehicle: 2001 Ford Escort ZX2 L4-2.0L DOHC VIN 3
Vehicle » Powertrain Management » Computers and Control Systems » Description and Operation » Standard Models (Non BI-Fuel) » Secondary AIR Monitor - Electric Secondary AIR Pump System  
  Secondary AIR Monitor - Electric Secondary AIR Pump System  

AIR System Monitor

The Secondary Air Injection (AIR) System Monitor is an on-board strategy designed to monitor the proper function of the secondary air injection system. The AIR Monitor for the Electric Secondary Air Injection Pump system consists of two monitor circuits: an AIR circuit to diagnose concerns with the primary circuit side of the Solid State Relay (SSR) , and an AIR Monitor circuit to diagnose concerns with the secondary circuit side of the SSR. 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 Heated Oxygen Sensor (HO2S) 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 Engine Coolant Temperature (ECT) , Intake Air Temperature (IAT) , and Crankshaft Position (CKP) sensors and the Heated Oxygen Sensors (HO2S) 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.

  1. The AIR circuit is normally held high through the AIR bypass solenoid and SSR 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 Powertrain Control Module (PCM) . The Diagnostic Trouble Code (DTC) associated with this test is DTC P0412.
  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 Powertrain Control Module (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.

  1. 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 HO2S 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 Diagnostic Trouble Code (DTC) P0411.

  1. The Malfunction Indicator Lamp (MIL) is activated after one of the above tests fail on two consecutive drive cycles.