This vehicle has electronic components which the service technician controls in order to provide valuable self-diagnostic information. These components are part of an electrical network that controls various engine subsystems and various body subsystems. A description of each of these subsystems is in the appropriate subsection of this service manual. These major components that compromise the computer system monitor the system sensors and the system switches. These components are the following:

The body control module (PZM) performs the following functions:

For more information about these functions refer to the appropriate sections.

The wake-ups are signals that turn ON the PZM. The signals cause active control or monitoring by the PZM.

The PZM wake-ups can include the following signals:

The afterblow function helps to removes condensation from the evaporator core.

The PZM begins a timed delay after the ignition is turned OFF. After the delay time elapsed, the PZM sends a serial data message to the heater and A/C programmer in order turn on the blower. After the afterblow function is complete, the heater and A/C programmer turns off the blower. Then the heater and A/C programmer than sends a serial data message to the PZM in order to enable the battery guard function.

The battery guard function provides protection from battery drain. The system includes the following functions:

The controlled power relay supplies power to the components under controlled power. The PZM does not control the high power control output. Instead, the output is grounded whenever the PZM is awake. The output also is grounded for 15 minutes after you turn the ignition switch to the LOCK position in order to obtain the RAP function. The following components are under controlled power:

1. The instrument cluster
2. The radio
3. The amplifier/radio interface module (RIM)
4. The cellular telephone (PHN)
5. The high beam relay
6. The fuel door release relay
7. The trunk release relay

After the 15 minutes elapse, the modules enter a sleepstate. The modules receive any necessary power from the low power driver output of the PZM. If the PZM is in the low power mode, and the PZM detects that the current exceeds approximately 2.4 amperes, the PZM wakes up and re-enters the high power mode. If the vehicle remains inactive with the ignition in the LOCK position and without any PZM wake-ups for a period of 3 days, the PZM deactivates the low power driver output.

The PZM automatically turns off the exterior lamps after 10 minutes if the headlamp switch remains ON after the ignition cycles to the LOCK or ACC position.

After 10 minutes, the PZM turns off inadvertent power in order to preserve battery power. The 10-minute timer starts after one of the following conditions is present:

If any of these conditions occur during the timer period, the timer resets to 10 minutes.

The Storage Mode allows the vehicle to be stored for long periods of time. The storage mode is enabled through the DIC. Twenty minutes after the storage mode has been enabled, the PZM disables both the low power and the high power relays. RFA functions are not available during storage mode and the PZM will set DTC B2250 as history.

The PZM energizes the door lock/unlock relays. This event occurs in the following conditions:

The RFA transmitter commands the following components:

The RFA module receives the command from the RFA transmitter. The RFA module then sends a serial data message to the PZM in order to perform the appropriate function.

When the PZM receives notification through the serial data line that the air bags have been deployed. The PZM automatically unlocks all of the doors and turnes on the interior lamps.

The PZM calculates the fuel level than sends a serial data message to the instrument cluster and the powertrain control module (PCM). The PZM sends the fuel level information to the instrument cluster each time there is a change of at least 0.5 liters (0.13 gallons). The PZM send the fuel level information to the PCM each time a change of 1.0 liter (0.26 gallons).

The RAP feature allows the operation of the following items after you turn the ignition switch from RUN to OFF positions:

These items turn off when one of the following conditions occurs:

A discrete inputs to the PZM arms and disarms the UTD. The UTD system detects unauthorized vehicle entry and cycles the horns and the exterior lamps on and off in order to deter theft.

The PZM can request the instrument cluster to display the flowing messages:

TRUNK OPEN

The PZM requests this message when the ignition switch is the RUN position and the trunk ajar input is active.

STORAGE MODE?

The PZM requests this message when you enter the vehicle personalization mode.

BATTERY STORAGE MODE ENABLED

The PZM requests this message when the PZM has entered the storage mode.

BATTERY STORAGE MODE TERMINATED

The the PZM requests this message when the storage mode has been disabled or when the PZM receives a negative response to the message STORAGE MODE?

AUTOMATIC DOOR LOCK?

The the PZM requests this message when you enter the vehicle personalization mode.

ENABLE ALL DOORS FOR LOCK AND UNLOCK?

The the PZM requests this message when you enter the vehicle personalization mode.

DISABLE ALL DOORS FOR LOCK AND UNLOCK?

The the PZM requests this message when you enter the vehicle personalization mode.

ENABLE ALL LOCKS AND DRIVER DOOR UNLOCK?

The the PZM requests this message when you enter the vehicle personalization mode.

ENABLE ALL LOCKS AND DRIVER DOOR UNLOCK?

The the PZM requests this message when you enter the vehicle personalization mode.

ENABLE ALL DOORS FOR LOCK ONLY?

The the PZM requests this message when you enter the vehicle personalization mode.

When the PZM requests the instrument cluster to display a driver waring or status message, the PZM also requests a chime appropriate for that message. The instrument cluster than sends a request to the radio to sound the chime. The one exception is the seat belt indicator ON, the PZM sends a class 2 request for a chime directly to the radio.

The PZM provides control for following exterior lighting items:

The instrument cluster sends all of the lamp on or off requests to the PZM on the class 2 serial data line. Except for of theft deterrent activation, the PZM controls theft deterrent activation.

The PZM provides control for following interior lighting items:

The following inputs enable the courtesy lamps:

The PZM only enables the illuminated entry control of the courtesy lamps when the instrument cluster twilight photocell indicates darkness.

When the PZM receives a serial data message for the activation of the trunk release solenoid from the instrument cluster or from the RFA, the PZM energizes the trunk release relay under the following conditions:

A real time clock internal to the PZM maintains the time of day. The broadcast of the time of day is as a class 2 message over the serial data line. The radio receives this data and displays the time of day data. Use the hour buttons and the minute buttons on the front of the radio in order to change the time of day. The radio sends a class 2 message to the PZM in order to change the time. The radio does not maintain the time.