Code
B1218
ALFA ROMEO
B — Body
Horn relay coil circuit
AI status
Completed
Completed
100%
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
Similar codes
Repair manuals
Manual library for ALFA ROMEO
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Code
B1218
FIAT
B — Body
Horn relay coil circuit
AI status
Completed
Completed
100%
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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Code
B1218
Other
B — Body
Horn Relay Coil Circuit Short to Vbatt
AI status
Completed
Completed
100%
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
Similar codes
Repair manuals
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