B109C

Code

LAND ROVER B — Body

Front courtesy light

Brand: LAND ROVER

Type: B — Body

Views: UK: 24 EN: 30 RU: 22

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Page language: EN

Causes

Blown or faulty courtesy light bulb (incandescent or LED)
Faulty front courtesy lamp assembly or internal connector corrosion
Open or shorted wiring between lamp and BCM (including damaged insulation)
Poor or corroded ground connection at lamp or body ground point
Faulty fuse or fusible link feeding the courtesy lamp circuit
Faulty BCM or software/firmware anomaly

Symptoms

Front courtesy/reading light does not illuminate with door open or switch operation
Light is intermittent (works sometimes, then not)
Light stays permanently on or off regardless of door/switch position
Related interior lighting behaves oddly (flicker, dim)
Possible related warning or BCM communication messages on scan tool

What to check

Read stored/active codes with an OBD/diagnostic scanner and freeze-frame data
Visually inspect front courtesy lamp assembly and bulb/LED for obvious damage or corrosion
Check related fuses and fusible links in fusebox for continuity
Operate lamp while probing with a multimeter to verify presence of supply voltage and ground
Inspect wiring harness along routing for chafe points, kinks, or connector damage (especially near doors and dash openings)
Check body grounds near the lamp and at common ground points for tightness and corrosion

Signal parameters

Expected supply voltage at lamp socket with circuit ON: ~11–14 V (battery voltage range)
Expected voltage with circuit OFF: near 0 V at lamp positive (or as BCM specifies) or open circuit depending on design
Typical incandescent courtesy lamp current: ~0.1–1.5 A (varies by bulb); LED modules draw far less (tens to hundreds of mA)
Resistance: incandescent bulb filament will show low ohms (a few ohms when cold); LED modules may show higher or semiconductor characteristics — refer to service data
CAN/BCM: BCM output command/status message present on network (verify with diagnostics tool)

Diagnostic algorithm

Connect diagnostic scanner, record B109C and any related codes, note freeze-frame and module data. Do not clear codes yet.
Verify symptoms: operate door switch and lamp switch while observing behavior and scanner live data for lamp control bits.
Visually inspect lamp assembly and bulb/LED. Replace bulb with known-good unit if inspection inconclusive; retest.
Check fuses related to interior lighting. Replace if blown and retest; if fuse blows again, stop and trace short.
With multimeter, measure voltage at the lamp positive terminal while operating the switch/door: expect ~11–14 V when commanded ON. If voltage present but lamp does not light, suspect lamp/connector.
Check continuity to ground at lamp negative. Wiggle harness/connectors and observe changes. Repair corroded/loose ground.
If no supply voltage at lamp when commanded ON, back-probe harness toward BCM to find loss point. Inspect connectors and splice points.
If wiring appears intact but no correct command from BCM, check CAN communication and BCM outputs with a diagnostic tool; verify BCM power and grounds.
If BCM output is confirmed faulty after wiring checks, refer to manufacturer procedures for BCM reflash/replacement and perform programming if required.
After repair, clear codes and perform functional tests (open/close doors, switch lamp on/off) and confirm no B109C reoccurs.

Likely causes

Burnt-out bulb or failed LED module
Loose, corroded, or disconnected connector at the lamp
Damaged harness (pinched/chafed) near door hinge or dash
Failed ground at lamp or nearby body ground stud

Fault status

⚠️ Status

Front courtesy light circuit fault detected (open/short/high resistance/BCM output anomaly). Verify lamp, wiring, grounds, fuse, and BCM.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 1.5 hours

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Browse 413 LAND ROVER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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