U02BF: Lost Communication With Interior Lighting Control Module B

What it means

The vehicle bus reports loss of communication with interior lighting control module B. Ambient lighting zones, reading lamps and door courtesy lights driven by this node fall back to a default state.

How it works

Interior lighting control module B switches the ambient lighting zones, reading lamps or door courtesy lights assigned to that node. The vehicle network monitors messages from module B and sets this code when they stop arriving or cannot be understood. The affected lights may be unavailable or remain in a default state.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan the body and network modules and save event data to see when interior lighting module B went offline and whether other body functions reported communication faults.
2. Operate the reading lamps, ambient zones and door courtesy lights assigned to module B while checking live data for module status or switch requests.
3. Inspect module B's connector and nearby wiring for looseness, corrosion, water entry or damage, paying attention to the affected door or cabin area.
4. Check the module's specified power and ground using the manufacturer's service information.
5. Test the bus wiring serving module B for opens, shorts or poor connections using the manufacturer's network procedure.
6. If supply and network checks pass, use the manufacturer's diagnostic process to test the module and verify the affected lights after repair.

Common fixes

• Reconnect or repair a loose or corroded connector at interior lighting control module B.
• Repair damaged bus wiring or restore the module's specified power or ground.
• Repair a damaged light or local wiring fault if checks show it is limited to one output rather than module communication.
• Replace or reprogram module B only if testing confirms the module has failed.

Can I keep driving?

The vehicle is generally safe to drive, but the lights controlled by module B may not work or may stay at a default setting. Before driving at night, check that needed cabin and door courtesy lighting is available and avoid relying on a failed courtesy light when entering or exiting.