Engine Start-Up (Cranking)

ENGINE START-UP
This is an OPEN LOOP MODE. The following actions occur when the starter motor is engaged:

1. The auto shutdown and high pressure fuel shut-off solenoid relays are energized. If the Powertrain Control Module (PCM) does not receive the camshaft and crankshaft signals within approximately one second, these relays are de-energized.
2. The PCM energizes all fuel injectors until it determines crankshaft position from the camshaft and crankshaft signals. The PCM determines crankshaft position within two engine revolutions. After the crankshaft position has been determined, the PCM energizes the fuel injectors in sequence. The PCM adjusts the injector pulse width and synchronizes the fuel injectors by controlling the fuel injectors ground paths.
3. Once the engine idles within 64 rpm of its target engine speed, the PCM compares the current MAP sensor value with the value received during the ignition switch on (zero rpm) mode. A diagnostic trouble code is written to PCM memory if a minimum difference between the two values is not found.

Once the auto shutdown and high pressure fuel shut-off solenoid relays have been energized, the PCM determines the fuel injector pulse width based on the following:
- Engine Coolant Temperature.
- Manifold Absolute Pressure.
- Engine Speed.
- Throttle Position.
- CNG Fuel Temperature.
- CNG Fuel Pressure.

The PCM determines the spark advance based on the following:
- Engine Coolant Temperature.
- Manifold Absolute Pressure.
- Engine Speed.
- Throttle Position.
- Crankshaft Position.
- Camshaft Position.