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.