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• After determining crankshaft position, the PCM begins energizing the injectors in sequence. It adjusts • When the engine idles within 664 RPM of its target RPM, the PCM compares current MAP sensor Once the ASD and fuel pump relays have been energized, the PCM determines injector pulse width • Battery voltage • Engine coolant temperature • Engine RPM • Inlet/Intake air temperature (IAT) • MAP • Throttle position • The number of engine revolutions since cranking was initiated During Start-up the PCM maintains ignition tim- ing at 9° BTDC. ENGINE WARM-UP MODE This is an OPEN LOOP mode. The following inputs are received by the PCM: • Engine coolant temperature • Manifold Absolute Pressure (MAP) • Inlet/Intake air temperature (IAT) • Crankshaft position (engine speed) • Camshaft position • Knock sensor • Throttle position • A/C switch • Battery voltage • Power steering pressure switch • Vehicle speed • Speed control • O2 sensors injector synchronization by turning the individual The PCM adjusts ignition timing and engine idle speed. Engine idle speed is adjusted through the idle CRUISE OR IDLE MODE When the engine is at operating temperature this is a CLOSED LOOP mode. During cruising or idle • Inlet/Intake air temperature • Engine coolant temperature • Manifold absolute pressure • Crankshaft position (engine speed) • Camshaft position • Knock sensor • Throttle position • Exhaust gas oxygen content • A/C control positions • Power steering pressure switch • Battery voltage • Vehicle speed injector synchronization by turning the individual The PCM adjusts engine idle speed and ignition timing. The PCM adjusts the air/fuel ratio according The PCM monitors for engine misfire. During active misfire and depending on the severity, the 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 • Purge system monitor • All inputs monitored for proper voltage range. • 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 sense • Battery voltage • Battery temperature • Engine coolant temperature • Engine run time • Inlet/Intake air temperature • Power steering pressure switch • Vehicle mileage ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog- nizes an abrupt increase in Throttle Position sensor JX FUEL SYSTEM 14 - 23 DESCRIPTION AND OPERATION (Continued) |