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MODES OF OPERATION As input signals to the Powertrain Control Module (PCM) change, the PCM adjusts its response to the output The PCM will operate in two different modes: Open Loop and Closed Loop. During Open Loop modes, the PCM receives input signals and responds only according to preset PCM program- During Closed Loop modes, the PCM will monitor the oxygen (O2S) sensors input. This input indicates to the PCM The fuel injection system has the following modes of operation: • Ignition switch ON • Engine start-up (crank) • Engine warm-up • Idle • Cruise • Acceleration • Deceleration • Wide open throttle (WOT) • Ignition switch OFF The ignition switch On, engine start-up (crank), engine warm-up, acceleration, deceleration and wide open throttle 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 • 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 approx- • The O2S sensor heater element is energized via the ASD relay. The O2S sensor input is not used by the PCM ENGINE START-UP MODE This is an Open Loop mode. The following actions occur when the starter motor is engaged. The PCM receives inputs from: • Battery voltage • Engine coolant temperature sensor • Crankshaft position sensor • Intake manifold air temperature sensor • Manifold absolute pressure (MAP) sensor • Throttle position sensor (TPS) • Starter motor relay • Camshaft position sensor signal The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position sensor signal 8E - 270 ELECTRONIC CONTROL MODULES - SERVICE INFORMATION WK |