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MALL Module Internal Diagnostic Procedures

The Body Control Module (MALL) provides a set of internal service diagnostic features to assist the technician in troubleshooting electrical short conditions that may affect the module. If an electrical short occurs during vehicle operation, the MALL module stores one or more codes (known as history codes). These codes may be accessed by entering the MALL module Diagnostic Mode. After providing the history codes, the MALL module enters the Input/Output (I/O) Mode. The I/O Mode provides the technician with the ability to verify that the inputs to the MALL module are functioning properly.

Entering the Diagnostic Mode
To enter the MALL module Diagnostic Mode, turn the ignition switch to ON, then perform the following procedure
1. Press and hold the power door unlock switch.
2. Cycle the headlamps six times. (Cycling of the Headlamp switch must occur within 20 seconds of pressing the unlock switch.)
3. Release power door unlock switch.

Exiting the Diagnostic Mode
To exit the Diagnostic Mode, turn the ignition switch to OFF or accelerate the vehicle above 13 km/h (8 mph).

History Codes
Upon entering the Diagnostic Mode, the MALL module provides audible feedback in the form of bongs; the number of bongs represents the stored history code number. The "FASTEN BELTS" indicator flashes with each bong.

History Codes:




The history code and its corresponding short circuit condition are as Shown in the figure.

The MALL module cycles through the stored history code(s) three times. For example, if a short condition occurs on the "FASTEN BELTS" indicator circuit and battery protection circuit, one bong sounds for the "FASTEN BELTS" indicator circuit, followed by two bongs for the battery protection circuit. A two second pause occurs before the history codes repeat. if no history codes exist, the MALL module immediately enters the Input/Output Mode.

The history codes may be erased by holding the power door unlock switch for four seconds.


Input/Output (I/O) Mode
While in the Input/Output (I/O) mode, the technician may test each input to the MALL module by activating/deactivating its input device (for example, door latch switch, interior lamp switch, seat belt switch, etc.). The MALL module provides feedback on each input transition in the form of a single bong along with a simultaneous flash of the "FASTEN BELTS" indicator.

Test the battery protection (PBATT) input/output by cycling the interior lamps switch. For example, the first cycle (OFF, ON, OFF) deactivates the PBATT output (interior lamps OFF). Cycling the interior lamp switch once again activates the PBATT output (interior lamps ON). The cycle repeats afterwards.

Unique I/O Mode Feed Back For Vehicles:




Unique I/O Mode Feedback For Vehicles Equipped With Keyless Entry

For vehicles with keyless entry, the MALL module electrical schematic differs from that of vehicles without keyless entry. For vehicles with keyless entry, the audible feedback is different when activating the power door lock switch, transaxle gear selector, and keyless entry unlock (using the keyless entry transmitter). The chart describes the feedback for this case.

Note that for Pontiac vehicles, no bongs occur when shifting into the PARK position due to the ignition-OFF door unlock feature.

Function/Feature/Test By Activating, Deactivating:




The table lists the MALL inputs and outputs that should be evaluated during the Input/Output (I/O) mode.
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