Courtesy Lamp: Description and Operation

PRINCIPLES OF OPERATION

NOTE:
- The dome lamp switch must be in the delay position to allow the dome lamp to function as illuminated entry or interior lamp.
- The FEM and REM must be reconfigured when installing a new module. Refer to Information Bus (Module Communications Network).

The vehicle electronic functions are divided into zones. The front electronic module (FEM) controls the front portion of the vehicle and the rear electronic module (REM) controls the rear portion of the vehicle. These systems rely heavily on the standard corporate protocol (SCP) communication network in order to transmit and receive signals. As a technician, it is very important to understand:
- where the input (command) originates from.
- all information (messages) necessary in order for a feature to operate.
- which module(s) receive(s) the input or command message.
- whether the module which received the input (message) controls the output of the feature, or whether it outputs a message over the SCP communication network to another module.
- which module controls the output of the feature.

FEM Operation
This system is unique in that many of the inputs the FEM receives are delivered via the SCP communication network. These input messages come from other modules connected to the network, such as the REM and the instrument cluster. The FEM interprets the inputs and then commands the correct output. The FEM also receives inputs directly from components which are hardwired to the module, such as the door ajar switches.

Interior Lighting
SSP 2 provides power through circuit 30-DD2 (RD/BU) between the BJB and the CJB. The interior lamp circuits are protected by CJB fuse 31 (10A). Power continues to the lamps through two circuits leaving the CJB. Circuit 29S-LC5 (OG/BU) supplies power to the auxiliary junction box (AJB) which connects to circuit 29S-LC11 (OG/WH) to the LH footwell lamp. Circuit 29S-LC1 (OG/BU) supplies power to a splice which splits into circuit 29S-LC23 (OG/WH) connecting to the RH footwell lamp and circuit 29S-LC8 (OG) connecting to the glove compartment lamp assembly.

SSP relay 4 provides power through circuit 30S-DB16 (RD/GN), which is internal to the BJB, to fuse 4 (10A). From the BJB, power is supplied through circuit 29-LB1 (OG/BU) to a splice where it splits into two circuits. Circuit 29S-LB19 (OG/BU) provides power to the dome/map lamp assembly and circuit 29S-LB25 (OG/BU) supplies power to the luggage compartment lamp.

The ground circuit from the dome lamp, circuit 9-LB14 (BN/BU), is spliced into circuit 9-LB19 (BN/RD). The ground circuits from the LH footwell lamp, circuit 31S-LC11 (BK/WH), and the RH footwell lamp, circuit 31S-LC23 (BK/WH), are spliced together to create circuit 31S-LC4 (BK/GN).

The interior lamps ground circuits 9-LB19 (BN/RD) and 31S-LC4 (BK/GN) connect to the interior AJB where they are combined into circuit 29S-LC3 (BK/RD) to the FEM. The FEM provides the remaining ground connection when a signal is received from one of the door ajar switches or the instrument panel dimmer switch.

The luggage compartment lamp is connected to the REM through circuit 31S-LB25 (BK/BU). The REM completes the ground circuit for the luggage compartment lamp when it receives a signal from the luggage compartment lid ajar switch on circuit 8-GL20 (WH/BK). The luggage compartment lid ajar switch is grounded to the LH rear panel ground through circuit 31-GL20 (BK/RD).

All interior lighting is powered by the switched system power (SSP) feature. A failure of any or all of the SSP feature(s) could cause inoperative interior lighting. When diagnosing the interior lighting, it is essential to determine if all relative symptoms and DTCs are controlled by the SSP feature.

Switched System Power (SSP)
The SSP is invoked by both the FEM and REM. This function removes power from relays that provide power to the exterior lamps, interior lamps, and power door locks. This is only accomplished when both the FEM and the REM are in sleep mode. The sleep function of the FEM and REM places the modules in sleep mode when the ignition switch is in the OFF position, and no wake up (inputs) signals occur for 30 minutes. The module will not sleep if the parking lamps or the hazard lamps are active. The following relays are controlled by the SSP function: SSP1, SSP2, SSP3, and SSP4. When either the FEM or REM are not in sleep mode, all SSP relays will be energized. Each relay, when energized, will supply power to multiple features/functions.