Ignition Switch (Key-On) Mode

This is an Open Loop mode. When the fuel system is activated by the ignition switch, the following actions occur: 

• The PCM pre-positions the idle air control (IAC) motor. 
• The PCM determines atmospheric air pressure from the MAP sensor input to determine basic fuel strategy. 
• The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based on this input. 
• Intake manifold air temperature sensor input is monitored. 
• Throttle position sensor (TPS) is monitored. 
• The auto shutdown (ASD) relay is energized by the PCM for approximately three seconds. 
• The fuel pump is energized through the fuel pump relay by the PCM. The fuel pump will operate for approximately three seconds unless the engine is operating or the starter motor is engaged. 
• The O2S sensor heater element is energized via the ASD relay. The O2S sensor input is not used by the PCM to calibrate air-fuel ratio during this mode of operation.