B1C43

Code

LAND ROVER B — Body

Switch main of the internal lamp

Brand: LAND ROVER

Type: B — Body

Views: UK: 22 EN: 34 RU: 27

AI status

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Page language: EN

Causes

Faulty main interior lamp switch (mechanical or electrical failure)
Open or shorted wiring in the switch circuit
Corroded, loose or damaged connector at the switch or body control module (BCM)
Poor ground or supply (blown fuse, poor earth connection)
Faulty interior lamp control module / BCM software or hardware fault
Intermittent contact due to moisture or foreign debris

Symptoms

Interior/dome lamp does not turn on when expected
Interior lamp stuck on or cannot be turned off (battery drain risk)
Lamp operates intermittently or only in certain positions
Warning message or lamp circuit fault stored in vehicle module
Other interior lighting functions (ambient/reading lights) may be affected

What to check

Scan vehicle and read stored/freeze-frame codes and module data (BCM/IPC)
Visually inspect interior lamp switch, connectors and surrounding harness for damage, corrosion or moisture
Check the interior lamp fuse(s) for continuity and correct rating
Operate the switch and observe lamp response while monitoring live data with a diagnostics tool
Backprobing: verify supply voltage and ground at the switch connector with a multimeter
Check continuity between switch and BCM and continuity to ground (with battery disconnected for continuity checks)

Signal parameters

Supply voltage to switch: ~12 V (battery voltage) with ignition/accessory or door open depending on vehicle logic
Switch output signal to BCM or lamp: 0 V (ground) or close to battery voltage depending on switch position and vehicle design
Expected continuity: closed switch ≈ 0–2 Ω across contacts, open switch = infinite/OL
Ground resistance:
Current draw: interior lamp circuits typically draw low to moderate current depending on lamp type (measure to confirm no excessive draw)

Diagnostic algorithm

Read and record DTC(s) and live data from the BCM or interior lighting module. Note freeze-frame data and any related codes.
Attempt to reproduce the fault: operate main interior lamp switch in all positions (ON, DOOR, OFF) and note behavior and any pattern.
Visually inspect switch assembly, headliner area, connectors and wiring for damage, moisture or corrosion. Repair visible damage.
Check the interior lighting fuse(s) for continuity and verify correct rating; replace if blown.
With a multimeter, measure supply voltage to the switch connector (battery voltage expected when circuit energized).
Measure ground quality at the switch and lamp earth points; clean and secure grounds if high resistance found.
Backprobe the switch output while operating the switch to confirm expected signal (voltage change or continuity to ground per design).
Check continuity from the switch connector to the BCM connector pins to rule out open/short in harness (inspect pin condition).
If wiring and supply/ground are good, perform functional test or swap with a known-good switch (if available) to isolate switch vs module.
If the switch tests good but fault persists, check BCM inputs/outputs for proper operation and update module software if recommended by manufacturer. Consider replacing BCM only after wiring and switch are verified faulty.
Clear codes and retest road/operate cycles to confirm repair; monitor for reoccurrence.

Likely causes

Failed interior lamp switch (button/stalk/module)
Damaged wiring harness at door/headliner area causing open/short
Poor ground at lamp/switch or blown fuse
Corroded connector at switch or BCM

Fault status

⚠️ Status

Stored — fault detected in main interior lamp switch circuit (electrical/communication fault). Further electrical checks required; may cause interior lamp inoperative or uncontrolled operation.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

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LAND ROVER

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