2005 Malibu Maxx. 1. Reverse lights won't stay on. They flicker or won't come on at all. 2. AC only works on 3. 4. The car locks and unlocks constantly when the car is in park.

Do you know how these thing's work ? How to do automotive electrical testing using a DVOM - digital volt ohm meter ? How to look up wiring diagrams to see what is involved in the working's of these systems ?

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Backup Lamps
The R-BEC 1 fuse in the underhood fuse block supplies battery positive voltage to the BACKUP LAMP relay through the BACKUP LAMP fuse. When the gear selector is placed in reverse, the body control module (BCM) supplies ground to the BACKUP LAMP relay. This energizes the BACKUP LAMP relay and current flows from the BACKUP LAMP relay to the backup lamps and then to ground. The backup lamps are grounded at G401 and G403.

The transmission range (TR) switch is part of the park/neutral position (PNP) and back-up lamp switch assembly (1), which is externally mounted on the transmission manual shaft. The TR switch contains four internal switches that indicate the transmission gear range selector lever position. The PCM supplies ignition voltage to each switch circuit. By grounding one or more of the switch circuits, the PCM detects the selected gear range by the state change of the switch input. Refer to Transmission Range Switch Logic . Switch input to the PCM is represented on the scan tool as HI and LOW. HI indicates an ignition voltage signal. LOW indicates a zero voltage signal. The four parameters represent transmission range switch signal A,B,C and Parity.

When the transmission is placed into reverse a input to the engine computer is received . The PCM - engine computer sends a massage on the C.A.N serial data network to the BCM - body control module . Which then energizes the back up lamps relay .

Same with the Door locks , controlled by the BCM .

Door Lock System Components
The Power Door Lock System consists of the following components:
• Body control module (BCM)
• Driver door lock switch
• Front passenger door lock switch
• Door lock actuators in each of the doors
• IBCM (PWR) 15-amp fuse
Door Lock System Controls
The Power Door Lock System is controlled by the body control module (BCM) and can be activated by any one of the following:
• A door lock switch Lock or Unlock actuation
• A keyless entry transmitter actuation
• An automatic door lock actuation
• An automatic door unlock actuation
• A last door closed locking (LDCL) actuation

A/C only works on 3,4 . we assume you mean the blower motor only works on med speed an high speed . This would be for the heat as well . Manual or automatic cilmate control ? The blower motor control module is probably at fault !

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Door Locks Go Crazy 1 The BCM is receiving false input's for bad door sensor or switch .