B1218

Code

ALFA ROMEO B — Body

Horn relay coil circuit

Brand: ALFA ROMEO

Type: B — Body

Views: UK: 6 EN: 7 RU: 7

AI status

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Page language: EN

Causes

Blown fuse for horn/relay circuit
Faulty horn relay (coil open or shorted)
Open or shorted wiring between relay and control module or power source
Poor or corroded connector/terminal at relay, horn or ground
Faulty horn switch (steering wheel) or clock spring/airbag connector problem
Failed body control module (BCM) or instrument cluster driver

Symptoms

Horn does not sound when horn button pressed
Horn works intermittently or only after tapping relay
No relay click when horn button pressed
Relay stuck on (horn sounding continuously) — less common
Related body module warnings or stored DTCs

What to check

Scan vehicle and read all related body/BCM codes; note freeze frame or events
Visually inspect relay, fuse, wiring harness and connectors for damage or corrosion
Check horn fuse for continuity and proper amperage
Swap horn relay with a known-good same-type relay and re-test
Listen for relay click when horn button pressed; probe relay coil terminals with a test light/multimeter
Directly apply 12 V to horn to verify horn itself is operational

Signal parameters

Relay coil activation voltage: approximately battery voltage (~9–14 V) on the supply terminal when powered
Control side may be switched to ground by BCM; expect near 0 V on control terminal when activated (if switched to ground)
Typical relay coil resistance: commonly in range 50–200 Ω (varies by relay); compare to service data or a known-good relay
Continuity: fuse and power feed to relay should show continuity to battery feed; ground continuity from relay return to chassis
No high-resistance spikes or intermittent open readings during repeated activation

Diagnostic algorithm

Record DTC and any related codes with a scan tool; clear codes to confirm reappearance.
Visually inspect relay, fuse, horn connectors, wiring and steering wheel area (clock spring) for damage, corrosion or loose pins.
Verify fuse protecting horn circuit has continuity and correct rating; replace if blown and retest.
Swap the horn relay with an identical, known-good relay in the fuse/relay box; test horn operation.
Back-probe relay coil terminals while pressing horn: verify supply voltage on one terminal and control (ground or switched voltage) on the other when activated.
If no control signal, check continuity from relay control terminal to BCM connector; inspect BCM grounds and pins.
If control signal is present but relay coil not energizing, remove relay and measure coil resistance. Replace relay if coil open/short.
If relay and wiring are good but horn still inoperative, apply 12 V directly to horn to confirm horn function; repair/replace as required.
Inspect/repair any damaged wiring, clean/replace corroded connectors, and repair poor grounds. Protect repaired areas against moisture.
If wiring and components are confirmed good and correct signals are present but DTC persists, test BCM output or seek module programming/replace per manufacturer procedures.
After repairs, clear codes, re-test horn operation and perform a road/functional check to ensure fault does not return.

Likely causes

Faulty or intermittent horn relay
Open/short in wiring to relay coil (connector corrosion or damage)
Blown fuse protecting horn circuit
Poor ground at horn or relay return
Control output from BCM not present or intermittent

Fault status

⚠️ Status

Horn relay coil circuit fault detected — open/short/incorrect voltage or intermittent connection in the horn relay coil circuit. Repair wiring, connectors, relay or control module as required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-1.5 hours

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