Engine Start-Up Mode

This is an open loop mode.

If the vehicle is in park or neutral (automatic transaxles) or the clutch pedal is depressed (manual trans axles) the ignition switch energizes the starter relay. 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) and fuel pump relays. If the PCM does not receive both signals within approximately one second, it will not energize the ASD relay and fuel pump relay. The ASD and fuel pump relays supply battery voltage to the fuel pump, fuel injectors, ignition coil and heated oxygen sensors.

- The PCM energizes all four fuel injectors (on the 69 degree falling edge) for a calculated pulse width 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. It 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 in memory.

Once the auto shutdown and fuel pump relays have been energized, the PCM determines the fuel injector pulse width based on:
- Engine Coolant Temperature
- Manifold Absolute Pressure
- Intake Air Temperature
- Engine Speed (RPM)
- Throttle Position
- Battery voltage
- The number of engine revolutions since cranking was initiated

During Start-up -- The PCM maintains ignition timing at 9° BTDC.