If a malfunction occurs in a system monitored by the BCM, the BCM stores a diagnostic trouble code (DTC) in memory. A current DTC means that the fault is present when the diagnostic mode was entered. Current DTCs are displayed with a beginning number 2 (2X). A history DTC means that the fault occurred sometime after the DTCs were last cleared from the BCM memory. History DTCs are displayed with a beginning number 3 (3X).

The DTCs are displayed as flash codes through the security indicator lamp on the instrument cluster when the BCM is in diagnostic mode. Perform the following steps in order to enter the BCM diagnostic mode:

1. Turn the ignition switch to the RUN position.
2. Turn the ignition switch to the OFF position.
3. Remove the Radio fuse from the I/P fuse block.
4. Turn the ignition switch to the ACCY position.
5. The BCM sounds 1 or 2 audible warning tones.
6. Within five seconds, turn the ignition switch to the OFF position and immediately (within 1 second) back to the ACCY position.
7. The BCM sounds 3 audible warning tones.

The BCM will begin flashing trouble codes using the security indicator 4 seconds after entering the diagnostic mode. Each series of quick flashes followed by a pause of the security indicator lamp on the instrument cluster represents a number in a 2 digit DTC. Each 2 digit DTC is displayed three times before the next DTC is displayed. DTCs are displayed in numerical order. Once the last DTC is displayed, the list begins again with the first DTC. This display rotation continues until the diagnostic mode is exited.

In the diagnostic mode, diagnostic trouble codes (DTCs) are displayed in the following order:

1. DTC 12

This indicates that the BCM is in diagnostic mode.

2. Any current DTCs (21 to 25) then any history DTCs (31 to 35)

These are displayed in numerical order.

3. The remote control door lock transmitter diagnostic DTCs (41 to 45)

These DTCs will display if the keyless entry transmitter buttons are pressed while in the diagnostic mode.

4. The begin configuration display (DTC 55)

DTC 55 and 2 single digit configuration numbers are always displayed. The first digit following DTC 55 is the hardware configuration. The second digit is the software configuration.

5. After the configuration numbers are displayed, the entire list is repeated beginning with DTC 12.

If only DTC 12, DTC 55 and the configuration digits are displayed when the BCM is in the diagnostic mode, the BCM has no circuit failure DTCs set and is operating properly.

If DTCs are not displayed, or if the BCM cannot enter the diagnostic mode, refer to Cannot Enter BCM Diagnostics .

If any other DTCs are displayed, refer to Diagnostic System Check - Body Control System .

Lock Test

While in diagnostic mode, if either door lock switch is pressed, the BCM will flash the fasten seat belt indicator on the instrument cluster and sound an audible warning tone. The BCM will also attempt to perform the operation normally performed by the switch operation. In this case, as long as the system is functioning properly, the BCM will lock the doors. This is a way to test the door lock actuators, switches and associated wiring without removing the door trim or components.

Tamper Sensors Test

The BCM will also respond to a change at either shock sensor input. The tamper input is activated by minor blows to the vehicle. The shock input is activated by heavy blows. In the diagnostic mode either the tamper input or the shock input will cause the BCM to activate the horn relay, and the horns will sound. The BCM will also flash the fasten seat belt indicator on the instrument cluster and sound an audible warning tone. An effective method of checking the shock sensor and associated wiring is to tap on the shock sensor while in the diagnostic mode.

Theft Deterrent Outputs Test

Switching the interior lamps switch on and off while in the diagnostic mode will cause the BCM to flash the fasten seat belt indicator on the instrument cluster, sound an audible warning tone, and flash the courtesy lamps. On vehicles equipped with theft deterrent, each transition of the interior lamps command input will cause the BCM to proceed to the next action in the following list:

1. The courtesy lamps flash
2. The horns sound
3. The exterior lights flash

Current DTCs (21 to 25) are displayed in the diagnostic mode as long as the BCM detects the fault. Once the fault is corrected, the current DTCs are cleared by the BCM.

To clear history DTCs (31 to 35) press and hold the door unlock switch for four seconds while the BCM is in the diagnostic mode. The BCM will sound three audible warning tones to confirm that the DTCs are cleared.

To clear BCM history DTCs (31 to 35) on vehicles without power door locks, back probe the position for the door unlock signal input with a fused jumper to ground for four seconds. The BCM will sound three audible warning tones to confirm that the history DTCs have been cleared.

Perform the following to leave diagnostic mode:

1. Turn the ignition switch to OFF.
2. Reinstall the Radio fuse in the IP fuse panel.
3. Turn the ignition to RUN.