Engine Start-Up (Cranking)

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 ASD relay and fuel pump relay. These relays supply battery voltage to the fuel pump, fuel injectors, ignition coil, and oxygen sensor heating element. If the PCM does not receive the camshaft position sensor and crankshaft position sensor signals within approximately one second, it de-energizes the ASD relay and fuel pump relay.

The PCM energizes all injectors until it determines crankshaft position from the camshaft position sensor and crankshaft position sensor signals.

The PCM determines crankshaft position within 1 engine revolution.

After determining crankshaft position, the PCM begins energizing the injectors in sequence. The PCM adjusts injector pulse width and controls 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 MAP diagnostic trouble code into memory

Once the ASD and fuel pump relays have been energized, the PCM:

- Determines injector pulse width based on engine coolant temperature, MAP and the number of engine revolutions since cranking was initiated.

- Monitors the engine coolant temperature sensor, cam shaft position sensor, crankshaft position sensor, MAP sensor, and throttle position sensor to determine correct ignition timing.