Ford Fiesta Quiz
Instrumentation and Warning Systems

Horn - Diagnosis and Testing

In this manual: Instrumentation and Warning Systems
Service Information — 27Suspension — 48Transmission — 9Brake System — 52Steering — 21Engine — 140Manual Transmission, Clutch, Transfer Case and Power Transfer Unit — 48Exhaust System — 6Fuel System — 21Climate Control System — 58Instrumentation and Warning Systems — 26Battery and Charging System — 20Infotainment Systems — 41Lighting — 29Power Distribution — 11Electronic Function Group — 30Body and Paint — 275Frame and Mounting — 3
~8min read

DTC Chart(s)

DTC Chart: Horn

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).


Body Control Module (BCM) Diagnostic Trouble Code Chart


Trouble Code Description Action
B1323:23 Horn Switch: Signal Low GO to Pinpoint Test B

Symptom Chart

Horn Symptom Chart

The diagnosis in this manual assumes a certain level of skill and knowledge of Ford-approved diagnostic procedures.
REFER TO: Diagnostic Methods (100-00 General Information, Description and Operation).


Symptom Chart


Condition Possible Sources Action
Horn does not sound Refer to Pinpoint Test GO to Pinpoint Test A
Horn is always on Refer to Pinpoint Test GO to Pinpoint Test B

Pinpoint Tests

Diagnostic Overview

Horn does not sound


For circuit and connector information, refer to Wiring Diagrams Cell 44.

Normal Operation and Fault Symptoms


Refer to: Horn - System Operation and Component Description (413-06 Horn, Description and Operation).

Possible Causes

  • Fuse
  • Wiring, Terminals or Connectors
  • Clockspring
  • Horn
  • Steering Wheel Wiring Harness
  • Driver Airbag (including horn switch)
  • BCM

Visual Inspection and Preliminary Diagnosis

  • Inspect fuse BJB 38 (20A).

DIAGNOSTIC PINPOINT TEST A: HORN INOPERATIVE
A1 CHECK THE BCM (BODY CONTROL MODULE) HORN OUTPUT USING THE HORN OUTPUT (SIGNAL) PID (PARAMETER IDENTIFICATION)
  • The ignition is on.
  • Using the diagnostic scan tool, view the BCM parameter identification (PID) data.
  • Select the BCM HORN active command PID. Command the horn ON, then OFF.

Does the horn sound on command?
Yes GO to A7
No GO to A2
A2 CHECK THE HORN SIGNAL VOLTAGE USING THE HORN OUTPUT (SIGNAL) PID (PARAMETER IDENTIFICATION)
  • Ignition OFF.
  • Disconnect: Horn C131.
  • The ignition is on.
  • Using the diagnostic scan tool, view the BCM parameter identification (PID) data.
  • Select the BCM HORN active command PID. Turn the horn on.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C131-2 Ground

Is the voltage greater than 11 volts?
Yes Turn the horn off. GO to A3.
No Turn the horn off. GO to A4.
A3 CHECK THE HORN GROUND CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C131-1 Ground

Is the resistance less than 3 ohms?
Yes INSTALL a new horn.
Refer to: Horn (413-06 Horn, Removal and Installation).
No REPAIR the circuit.
A4 CHECK THE BATTERY VOLTAGE AT THE BCM (BODY CONTROL MODULE)
  • Ignition OFF.
  • Disconnect: BCM C2280A.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C2280A-3 Ground

Is the voltage greater than 11 volts?
Yes GO to A5
No CHECK that BJB fuse 38 (20A) is OK. If OK, REPAIR the open circuit. If not OK, REFER to the wiring diagrams to determine the possible causes of the short circuit.
A5 CHECK THE HORN VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C2280A-2 C131-2

Is the resistance less than 3 ohms?
Yes GO to A6
No REPAIR the circuit.
A6 CHECK THE HORN VOLTAGE SUPPLY CIRCUIT FOR A SHORT TO GROUND
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C131-2 Ground

Is the resistance greater than 10000 Ohms?
Yes GO to A14
No REPAIR the circuit.
A7 CHECK FOR A HORN SWITCH INPUT
  • Ignition OFF.
  • Disconnect: BCM C2280E.
  • While pressing the horn, measure:
    Press to display connectors
    Positive lead Measurement/Action Negative lead
    C2280E-1 Ground

Is the resistance less than 3 ohms?
Yes GO to A14
No GO to A8
A8 CHECK HORN OPERATION WITH THE HORN SWITCH CIRCUITS DISCONNECTED
  • Connect: BCM C2280E.
  • Disconnect: Clockspring C218B.
  • Connect a fused jumper wire:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C218B-11 Ground

Does the horn sound?
Yes REMOVE the fused jumper. GO to A10.
No REMOVE the fused jumper wire. GO to A9.
A9 CHECK THE HORN SWITCH CIRCUIT FOR AN OPEN
  • Disconnect: BCM C2280E.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C2280E-1 C218B-11

Is the resistance less than 3 ohms?
Yes REPAIR the horn switch ground circuit GD116 (BK/VT).
No REPAIR the open horn switch circuit.
A10 CHECK THE HORN SWITCH GROUND CIRCUIT FOR AN OPEN
  • Disconnect: BCM C2280E.
  • Connect: Clockspring C218B.
  • Remove the driver air bag.
    REFER to: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217A-1 C2280E-1

Is the resistance less than 3 ohms?
Yes GO to A11
No GO to A12
A11 CHECK THE HORN SWITCH GROUND CIRCUIT
  • Ignition OFF.
  • Disconnect the horn switch C217B.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217B-1 Ground

Is the resistance less than 3 ohms?
Yes INSTALL a new driver air bag (including the horn switch).
Refer to: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
No GO to A13
A12 CHECK THE HORN SWITCH CIRCUIT IN THE STEERING WHEEL WIRING HARNESS
  • Disconnect: Clockspring C218C.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217A-1 C218C-4

Is the resistance less than 3 ohms?
Yes INSTALL a new clock spring.
Refer to: Clock Spring (501-20B Supplemental Restraint System, Removal and Installation).
No INSTALL a new steering wheel (including the steering wheel wiring harness).
Refer to: Steering Wheel (211-04 Steering Column, Removal and Installation).
A13 CHECK THE HORN SWITCH GROUND CIRCUIT IN THE STEERING WHEEL WIRING HARNESS
  • Disconnect: Clockspring C218C.
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217B-1 C218C-8

Is the resistance less than 3 ohms?
Yes INSTALL a new clock spring.
Refer to: Clock Spring (501-20B Supplemental Restraint System, Removal and Installation).
No INSTALL a new steering wheel (including the steering wheel wiring harness).
Refer to: Steering Wheel (211-04 Steering Column, Removal and Installation).
A14 CONFIRM THE BCM (BODY CONTROL MODULE) IS THE CAUSE
  • Ignition OFF.
  • Inspect the BCM connectors.
  • Repair:
    • corrosion (install new connector or terminals - clean module pins)
    • damaged or bent pins - install new terminals/pins
    • backed-out pins - install new pins as necessary
  • Connect: Horn C131 (if previously disconnected).
  • Connect: BCM C2280A (if previously disconnected).
  • Connect: BCM C2280E (if previously disconnected).
  • Make sure all connectors are properly installed and fully latched.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable technical service bulletins (TSBs). If a TSB exists for this concern, STOP this test and FOLLOW the TSB instructions. If no TSBs apply to this concern, INSTALL a new BCM.
REFER TO: Body Control Module (BCM) (419-10 Multifunction Electronic Modules, Removal and Installation).
No The system is currently operating correctly. The concern may have been caused by module connections. ADDRESS the root cause of any connector or terminal issues.

Diagnostic Overview

Horn is always on


For circuit and connector information, refer to Wiring Diagrams Cell 44.

Normal Operation and Fault Symptoms


Refer to: Horn - System Operation and Component Description (413-06 Horn, Description and Operation).


Diagnostic Trouble Code Chart


Trouble Code Description Fault Trigger Condition
B1323:23 Horn Switch: Signal Low The fault is displayed when the BCM detects a pressed horn switch or a short to ground on the horn switch signal circuit for more than 120 seconds. This DTC is also set if the horn switch is pressed during the BCM self-test.

Possible Causes

  • Wiring, Terminals or Connectors
  • Clockspring
  • Steering Wheel Wiring Harness
  • Driver Airbag (including horn switch)
  • BCM

DIAGNOSTIC PINPOINT TEST B: HORN ALWAYS ON
B1 ISOLATE THE HORN SWITCH AND CIRCUITS
  • Ignition OFF.
  • Disconnect: BCM C2280E.

Does the horn remain on?
Yes GO to B2
No GO to B3
B2 ISOLATE THE BCM (BODY CONTROL MODULE)
  • Disconnect: BCM C2280A.

Does the horn remain on?
Yes REPAIR the CRH04 (VT/GN) electrical circuit for a short to voltage supply.
No GO to B6
B3 ISOLATE THE HORN SWITCH
  • Remove the driver air bag.
    REFER to: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
  • Connect: BCM C2280E.

Does the horn remain on?
Yes DISCONNECT BCM C2280E. GO to B4.
No DISCONNECT the BCM C2280E. INSTALL a new driver air bag (including the horn switch).
REFER TO: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
B4 CHECK THE HORN SWITCH SIGNAL CIRCUIT FOR A SHORT TO GROUND
  • Disconnect: Clockspring C218B.
  • Connect: BCM C2280E.

Does the horn remain on?
Yes REPAIR the circuit.
No DISCONNECT the BCM C2280E. GO to B5
B5 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND
  • Connect: Clockspring C218B.
  • Disconnect: Clockspring C218C.
  • Connect: BCM C2280E.

Does the horn remain on?
Yes INSTALL a new clock spring.
Refer to: Clock Spring (501-20B Supplemental Restraint System, Removal and Installation).
No INSTALL a new steering wheel (including the steering wheel wiring harness).
Refer to: Steering Wheel (211-04 Steering Column, Removal and Installation).
B6 CONFIRM THE BCM (BODY CONTROL MODULE) IS FAULTY
  • Ignition OFF.
  • Inspect the BCM connectors.
  • Repair:
    • corrosion (install new connector or terminals - clean module pins)
    • damaged or bent pins - install new terminals/pins
    • backed-out pins - install new pins as necessary
  • Connect: BCM C2280A.
  • Connect: BCM C2280E.
  • Make sure all connectors are properly installed and fully latched.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable technical service bulletins (TSBs). If a TSB exists for this concern, STOP this test and FOLLOW the TSB instructions. If no TSBs apply to this concern, INSTALL a new BCM.
REFER TO: Body Control Module (BCM) (419-10 Multifunction Electronic Modules, Removal and Installation).
No The system is currently operating correctly. The concern may have been caused by module connections. ADDRESS the root cause of any connector or terminal issues.

Test yourself

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