Principles Of Operation

Interior Lighting

Principles of Operation

The Body Control Module (BCM) controls all the interior lighting functions and timing by monitoring inputs from the following:

- door ajar switches

- liftgate ajar switch (manual liftgate)

- Liftgate/Trunk Module (LTM) (power liftgate)

- ignition state

- Front Lighting Control Module (FLM)

- Remote Keyless Entry (RKE) system

- vehicle speed

The BCM (Body Control Module) turns off the courtesy lamps when the vehicle speed exceeds 15 km/h (9 mph) or 5 km/h (3 mph) for the puddle lamps, unless the courtesy lamps are turned on using the instrument panel dimmer switch (integrated into the FLM (Front Lighting Control Module)).

Interior Lamp Arbitrator

The interior lamp arbitrator (programming within the BCM (Body Control Module)) chooses between the interior lighting delay, the illuminated entry and exit, the battery saver, and the alarm flash processing to determine which feature has precedence of activating and deactivating the interior lamps.

Ambient Lighting

The HVAC module controls the ambient lighting system. When requested, the HVAC module provides voltage and ground to the LEDs. There are 3 LEDs (Edge) (red, blue and green) or 4 LEDs (MKX) (red, blue, green and white) housed within each LED assembly. By illuminating various color combinations, the LEDs are able to produce 7 different colors of ambient light.

The HVAC module receives input from the Accessory Protocol Interface Module (APIM) and the Body Control Module (BCM) over the communication network for color and brightness settings.

The display interface in the center of the instrument panel is used to cycle through different color variations or turn the ambient lighting feature on or off. The APIM (Accessory Protocol Interface Module) communicates messages over the High Speed Controller Area Network (HS-CAN) to the Body Control Module (BCM).

The BCM (Body Control Module) gateways the messages to the HVAC module over the Medium Speed Controller Area Network (MS-CAN). The HVAC module retains the last color and brightness setting between uses.

Field-Effect Transistor (FET) Protection

A Field-Effect Transistor (FET) is a type of transistor that, when used with module software, monitors and controls current flow on module outputs. The FET (Field-Effect Transistor) protection strategy prevents module damage in the event of excessive current flow.

The BCM (Body Control Module) utilizes an FET (Field-Effect Transistor) protective circuit strategy for many of its outputs (for example, a headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A short circuit DTC is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the FET (Field-Effect Transistor) circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (FET (Field-Effect Transistor) protection) and the circuit is still shorted, the FET (Field-Effect Transistor) protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. Each FET (Field-Effect Transistor) protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the FET (Field-Effect Transistor) and the ability of the FET (Field-Effect Transistor) to withstand it. A module lifetime level of fault events is established based upon the durability of the FET (Field-Effect Transistor). If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the short circuit DTC that was stored on the first failure cannot be cleared by a command to clear the continuous DTCs. The module does not allow this code to be cleared or the circuit restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand DTCs present), DTC U1000:00 and the associated DTC (the DTC related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the DTC associated with the short circuit sets along with DTC U1000:00. These DTCs are cleared using the module on-demand self-test, then the Clear DTC operation on the scan tool (if the on-demand test shows the fault corrected). The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then DTCs U1000:00 and U3000:49 set along with the associated short circuit DTC. DTC U3000:49 cannot be cleared and the module must be replaced after the repair.

The BCM (Body Control Module) FET (Field-Effect Transistor) protected output circuits for the interior lighting system are the interior courtesy lamp and puddle lamp output circuits.