Engine Start-Up

This is an OPEN LOOP mode. The following actions occur when the starter motor is engaged.

If the PCM receives the camshaft position sensor and crankshaft position sensor signals, it energizes the auto shutdown (ASD) relay and fuel pump relay. These relays supply battery voltage to the fuel pump, fuel injectors, ignition coil, and the heating element in each oxygen sensor. If the PCM does not receive signals from both sensors within approximately one second, it opens the ASD and fuel pump relays.

The PCM determines crankshaft position from the camshaft position sensor and crankshaft position sensor signals. The PCM determines crankshaft position within 1 engine revolution. Following instructions from the PCM, the ICM grounds the electronic ignition coils in sequence.

After determining crankshaft position, the PCM and ICM begin energizing the injectors in sequence. The PCM and ICM adjust injector pulse width and control injector synchronization by turning the individual ground paths to the injectors On and Off.

When the engine idles within 64 RPM of its target RPM, the PCM compares current MAP sensor value with the atmospheric pressure value received during the, Ignition Switch On (Zero RPM) mode. If the PCM does not detect a minimum difference between the two values, it sets a diagnostic trouble code into memory.

Once the ASD and fuel pump relays energize, the PCM determines injector pulse width based on following:

• Engine Coolant Temperature
• Engine RPM
• The Number Of Engine Revolutions Since Cranking Was Initiated