Theory Of Operation

The PCM receives voltage on the dedicated wake up signal from the BCM to turn on and become active. The wake up signal voltage must be above approximately 5.0 volts for the PCM to recognize it as a valid signal. The wake up is sent for all of the following reasons:

• The ignition is turned on.
• A refueling event is being requested.
• The Evaporative System diagnostics need to be performed (This occurs six hours after the ignition is turned off).

When the wake up signal is sent, the BCM will send a corresponding bus message with the reason for the signal to the PCM. If the PCM receives the wake up signal without one of the above corresponding messages from the BCM, a fault is set.