B1C89

Code

LAND ROVER B — Body

Inverting lamps retransmit output circuit

Brand: LAND ROVER

Type: B — Body

Views: UK: 21 EN: 34 RU: 28

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Page language: EN

Causes

Open or short in lamp output wiring (to battery or ground)
Corroded, loose or damaged connector at lamp or module
Failed lamp/bulb or LED unit
Defective body control module (BCM) or lamp driver transistor
Blown fuse or faulty relay in lamp circuit
Water ingress or corrosion in lamp housing or connector

Symptoms

Affected exterior lamp(s) do not illuminate or are intermittent
Lamp brightness incorrect (flicker, dim, or stuck on)
One or more lighting-related warnings or indicator lamps on dash
Related functions (auto lights, DRL, turn signals) may be impaired
DTC B1C89 present in fault memory; possible multiple lamp DTCs

What to check

Use a diagnostic scanner to read fault codes, freeze frame and lamp status; note any related codes
Visually inspect lamp housings, connectors and wiring for corrosion, damage or water ingress
Check relevant fuses and relays for continuity and correct rating
With ignition on, command the lamp output on/off using a scan tool and observe behavior
Measure voltage at the lamp connector with output commanded on and off
Perform continuity and short-to-ground checks between module connector and lamp

Signal parameters

Expected: ~0 V (off) and ~battery voltage (on) at lamp supply for conventional bulbs
LED lamps: lower steady current draw; module may use PWM to control brightness
PWM duty cycle varies when dimming/DRL; frequency depends on vehicle (typically 100 Hz to several kHz)
Current draw: halogen bulbs several hundred mA to a few amps; LED modules typically tens to a few hundred mA
A retransmit/feedback circuit may present a monitored voltage or resistance signal to the module when lamp connected

Diagnostic algorithm

Read and record all DTCs and freeze-frame data with a compatible scanner. Note related lighting or communication codes.
Visually inspect the affected lamp assembly, connector(s) and wiring for damage, corrosion, or water entry. Repair any obvious issues.
Verify fuses/relays in the lighting circuit. Replace any blown fuses and retest.
Using the scan tool, command the lamp output on/off. Observe the lamp and watch the live data for retransmit/feedback signal changes.
With output commanded on, measure voltage at the lamp connector. If no voltage, perform continuity check from module pin to lamp connector.
Check for shorts to battery or ground (insulation damage). Isolate the circuit (disconnect lamp) and measure output at module—if output still abnormal, suspect module driver.
Swap in a known-good lamp or harness to determine if the lamp assembly is faulty. Re-test the circuit.
If wiring and lamp are good but output is stuck or shows short/internal fault, suspect BCM/lamp driver. Check for software updates or reprogramming bulletins before replacement.
If BCM replacement is required, follow manufacturer procedures for module coding/programming and verify operation afterward.
Clear codes and perform a road/test cycle or functional tests to confirm repair. Re-scan to ensure no recurrence.

Likely causes

Corroded/damaged connector or wiring to the affected lamp
Failed lamp/LED unit or lamp harness shorted to body ground
BCM/lamp driver output damaged (open or shorted)
Blown fuse or poor ground at chassis/connector

Fault status

⚠️ Status

Lamp retransmit output circuit fault detected — check lamp, connector/wiring and module output.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0 - 2.5 hours

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