The Body Control Module (BCM) is capable of accomplishing multiple body control functions. Components directly connected to the BCM are controlled by the BCM's outputs. The BCM can control its outputs based on input information it obtains from sensors and switches that are directly connected to the BCM, or by borrowing information from other vehicle systems connected to the Class 2 serial data link. The BCM evaluates this information and controls certain body systems by commanding an output on or off.

The BCM is also capable of commanding other vehicle systems to control functions that are not directly wired and/or controlled by the BCM. The BCM accomplishes this task by sending specific messages on the Class 2 serial data link. The vehicle system capable of performing such function will respond to the BCM message.

The BCM performs these functions:

The Personal Automotive Security System (PASS-Key® II) is a vehicle theft deterrent system. The PASS-Key® II is designed in order to prevent vehicle theft by disabling the engine from starting unless an ignition key with a specific resistor pellet code is used in the ignition lock cylinder.

The ignition lock cylinder contains the resistor sensing contacts. These contacts touch the resistor pellet embedded in the ignition key. When the ignition key is inserted in the ignition lock cylinder, the resistor pellet completes the key detection circuit (CKT 1073 and CKT 1074).

When the ignition switch is turned from the OFF to the RUN position, the BCM applies a 5 V reference voltage to CKT 1073. The BCM reads the resistor pellet code and compares the stored resistor pellet code against the ignition key resistor pellet code for a correct match.

Upon detecting a correct match, the BCM sends a fuel enable password to the PCM through the Class 2 serial data link. As a result, the PCM enables the crank relay. This action allows fuel delivery to the engine.

If the key resistor pellet is incorrect, the PCM performs the following actions:

This vehicle disable period state lasts approximately 3 minutes. The SECURITY indicator flashes when the ignition switch is turned to the RUN position. Disconnecting the battery will not clear the timer sequence. The timer sequence resumes when the battery power is restored. If a proper key is inserted during the vehicle disable period, the vehicle will not start until the 3 minute time period elapses. After the 3 minute time period, the SECURITY indicator changes from a flashing state to a solid ON state. At this time, the BCM enters the theft deterrent re-learn mode. The engine will start if the correct ignition key resistor pellet is used.

Refer to Theft Deterent System Operation in Theft Deterent for more information.

The Accessory Power (RAP) feature allows the operation of the following functions for 10 minutes (or until a vehicle door opens) after the ignition switch has been turned from the ON or ACCESSORY position to the LOCK position:

Refer to Keyless Entry System Operation in Retained Accessory Power (RAP) for more information.

The BCM performs its functions in the wake-up state. The BCM enters the sleep state when active control or monitoring of system malfunctions has stopped, or when the BCM is idling. The BCM must detect certain wake-up inputs before entering the wake-up state. The BCM monitors its inputs during the sleep state, allowing the BCM to switch between the two states, awake or asleep.

The BCM enters the wake-up state when receiving activity on any of these inputs:

The sleep state is when the BCM has stopped active control and monitoring of system functions and has become idle again. For the BCM to enter the wake-up state, the BCM must detect a wake-up condition, mentioned previously. These conditions are called wake-up inputs that cause the BCM to change from a sleep to a wake-up state and begin active control and monitoring. The BCM has the ability to monitor for these wake-up inputs in the sleep state.

The BCM enters the sleep state when all of these conditions exist: