B1C55

Code

LAND ROVER B — Body

Coil circuit horn relay

Brand: LAND ROVER

Type: B — Body

Views: UK: 25 EN: 54 RU: 27

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Page language: EN

Causes

Blown fuse protecting the horn circuit
Faulty horn relay (coil open or shorted)
Poor or corroded relay socket/connector or wiring
Open or short to ground/power in the coil feed or control circuit
Faulty Body Control Module (BCM) or relay driver output
Intermittent connection due to wiring chafe or damaged insulation

Symptoms

Horn will not sound when activated
Horn may work intermittently or only after tapping relay
Relay may not click when horn switch is pressed
Possible blown fuse on repeated attempts to operate horn
DTC B1C55 stored and possibly related warnings/messages in dash

What to check

Scan vehicle and verify B1C55 is current; note freeze-frame/related codes
Visually inspect horn relay, fuse and relay socket for corrosion, heat damage or loose connections
Listen for relay click when horn is commanded (from steering wheel or using a scan tool)
Command the horn on with a diagnostic tool to observe behavior
Check supply fuse for continuity and battery voltage at the fuse/relay supply pin

Signal parameters

Supply voltage to relay coil: ~12 V (battery voltage) with ignition on
Control signal from BCM: ground-switched or switched 12 V depending on design (0 V to ~12 V when activated)
Expected coil resistance: typically in the range of ~50–200 ohms (varies by relay) — compare to factory spec
Activation current (approx): 0.05–0.3 A (dependent on coil resistance and relay design)
CAN/BUS: BCM should receive horn command message when steering horn switch pressed; loss of message may indicate communications fault

Diagnostic algorithm

Retrieve full code list and freeze-frame data. Note whether code is stored as active or historic and check for related communication codes.
Visually inspect the horn relay, fuse, relay socket and associated wiring for corrosion, melted insulation, loose terminals, or water ingress.
Verify fuse continuity and battery voltage at the fuse. Replace fuse if blown and retest (do not drive fused circuit repeatedly without diagnosing cause).
With ignition ON, command the horn using a scan tool while listening for relay click. If relay clicks but horn does not sound, suspect horn element or supply wiring to horn.
Back-probe relay socket: measure supply pin voltage (should be battery voltage), measure control pin while commanding horn (should switch to ground or 12 V depending on design).
Remove relay and measure coil resistance across coil pins with multimeter; compare to factory spec. If coil open or out of range, replace relay.
Bench-test suspect relay by applying appropriate coil voltage and verifying contact switching. Replace relay if it fails.
If control signal is not present or incorrect, trace wiring from relay control pin to BCM: check continuity, shorts to ground/power and connector pin condition. Repair wiring as required.
If wiring and relay are good, check BCM output driver using an oscilloscope or lab scope for intermittent faults or excessive current draw. Replace or reprogram BCM only after confirming external wiring and relay are serviceable.
Clear codes, perform functional test of horn several times, and road-test to verify repair. If intermittent, perform wiggle tests and re-check for stored codes over time.

Likely causes

Corroded relay socket pin or poor terminal contact
Relay coil internal fault (open/high resistance)
Blown/loose fuse supplying relay coil
BCM/relay module not supplying ground or switched voltage to coil
Damaged wiring between BCM and relay or between relay and fuse

Fault status

⚠️ Status

Fault detected in horn relay coil circuit (open, short, high resistance or intermittent) — relay may not energize.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2 hours

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