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instrument panel). Also, the PCM stores an engine The PCM performs several diagnostic routines. They include: • Oxygen sensor monitor • Downstream heated oxygen sensor diagnostics during open loop operation (except for shorted) • Fuel system monitor • EGR monitor (if equipped) • Purge system monitor • Catalyst efficiency monitor • All inputs monitored for proper voltage range, rationality. • All monitored components (refer to the Emission section for On-Board Diagnostics). The PCM compares the upstream and downstream heated oxygen sensor inputs to measure catalytic During certain idle conditions, the PCM may enter a variable idle speed strategy. During variable idle • A/C status • Battery voltage • Battery temperature or Calculated Battery Tem- perature • Engine coolant temperature • Engine run time • Inlet/Intake air temperature • Vehicle mileage ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog- nizes an abrupt increase in Throttle Position sensor • Wide Open Throttle-open loop DECELERATION MODE This is a CLOSED LOOP mode. During decelera- tion the following inputs are received by the PCM: • A/C status • Battery voltage • Inlet/Intake air temperature • Engine coolant temperature • Crankshaft position (engine speed) • Exhaust gas oxygen content (upstream heated oxygen sensor) • Knock sensor • Manifold absolute pressure • Throttle position sensor • IAC motor (solenoid) control changes in response to MAP sensor feedback The PCM may receive a closed throttle input from the Throttle Position Sensor (TPS) when it senses an WIDE-OPEN-THROTTLE MODE This is an OPEN LOOP mode. During wide-open- throttle operation, the following inputs are used by • Inlet/Intake air temperature • Engine coolant temperature • Engine speed • Knock sensor • Manifold absolute pressure • Throttle position tion through the Throttle Position Sensor (TPS) it de- The PCM adjusts injector pulse width to supply a predetermined amount of additional fuel, based on IGNITION SWITCH OFF MODE When the operator turns the ignition switch to the OFF position, the following occurs: • All outputs are turned off, unless 02 Heater Monitor test is being run. Refer to the Emission sec- • No inputs are monitored except for the heated oxygen sensors. The PCM monitors the heating ele- FUEL CORRECTION or ADAPTIVE MEMORIES DESCRIPTION In Open Loop, the PCM changes pulse width with- out feedback from the O2 Sensors. Once the engine 14 - 22 FUEL INJECTION PL/SRT-4 FUEL INJECTION (Continued) |