Ford Explorer Quiz
Electrical

Diagnosis and Testing - Horn

In this manual: Electrical
General Information — 41Chassis — 173Powertrain — 250Electrical — 303Body and Paint — 331
~12min read

Diagnostic Trouble Code (DTC) 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).


Diagnostic Trouble Code Chart


Module Trouble Code Description Action
BCM B1323:11 Horn Switch: Short to Ground GO to Pinpoint Test B
BCM B1C55:12 Horn Relay: Short to Battery GO to Pinpoint Test A
BCM B1C55:14 Horn Relay: Short to Ground or Open Circuit GO to Pinpoint Test A
BCM B1C55:14 Horn Relay: Short to Ground or Open Circuit 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 Diagnostic Test
  • GO to Pinpoint Test A
Horn is always on
  • Refer to Diagnostic Test
  • GO to Pinpoint Test B

Pinpoint Tests


DIAGNOSTIC TEST A: HORN INOPERATIVE

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

Normal Operation and Fault Symptoms

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

DTC Fault Trigger Conditions

Trouble Code Description Fault Trigger Condition
BCM B1C55:12 Horn Relay: Short to Battery Continuous Memory Diagnostic Trouble Code (CMDTC) that is set when the BCM detects a short to battery voltage in the horn relay control circuit. The BCM disables the horn when this trouble code is set.
BCM B1C55:14 Horn Relay: Short to Ground or Open This DTC is set when the BCM detects a short to ground or an open in the horn relay control circuit.

Possible Sources

  • Fuse
  • Wiring, Terminals or Connectors
  • Clockspring
  • SCCM
  • Horn
  • Horn Relay
  • Horn Switch
  • BCM
  • BCMC

Visual Inspection and Pre-checks

  • Make sure the BCM fuse 13 (7.5A) is good.
NOTICE: Use the correct probe adapter(s) when making measurements. Using incorrect probe adapter(s) may damage the connector.
A1 CHECK THE BCM (BODY CONTROL MODULE) OUTPUT WHEN THE BCM (BODY CONTROL MODULE) HORN_RELAY PID (PARAMETER IDENTIFICATION) IS ACTIVATED
  • The ignition is on.
  • Using the diagnostic scan tool, view the BCM parameter identification (PID) data.

  • Access the BCM and monitor the HORN_RELAY PID

    and command the horn ON, then OFF.

Does the horn sound when commanded ON?
Yes GO to A10
No GO to A2
A2 CHECK THE BCM (BODY CONTROL MODULE) DTC (DIAGNOSTIC TROUBLE CODE) B1C55:12 OR B1C55:14
  • The ignition is on.
  • Using a scan tool, perform the BCM self-test.
  • Using the diagnostic scan tool, perform the SCCM self-test.

Is DTC B1C55:12 or B1C55:14 present?
Yes For DTC B1C55:12 GO to A3
For DTC B1C55:14 GO to A5
No GO to A9
A3 CHECK THE BCM-C HORN RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
  • Ignition OFF.
  • Disconnect BCMC C1035A.
  • The ignition is on.
  • Action:
    Positive lead Measurement/Action Negative lead
    C1035A-20 Ground

Is there voltage present?
Yes GO to A4
No GO to A5
A4 DISCONNECT THE BCM-C HORN RELAY CONTROL CIRCUIT, SHORT TO VOLTAGE
  • Ignition OFF.
  • Disconnect the C2280F connector.
  • The ignition is on.
  • Action:
    Positive lead Measurement/Action Negative lead
    C1035A-20 Ground

Is there voltage present?
Yes REPAIR the circuit.
No GO to A17
A5 CHECK THE HORN RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
  • Ignition OFF.
  • Disconnect the C2280F connector.
  • Disconnect the battery negative cable.
  • Action:
    Positive lead Measurement/Action Negative lead
    C2280F-20 Ground

Is the resistance greater than 10000 Ohms?
Yes GO to A7
No GO to A6
A6 ISOLATE THE HORN RELAY CONTROL CIRCUIT SHORT TO GROUND
  • Disconnect BCMC C1035A.
  • Action:
    Positive lead Measurement/Action Negative lead
    C2280F-20 Ground

Is the resistance greater than 10000 Ohms?
Yes CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern, INSTALL a new BCMC.
Refer to: Body Control Module C (BCMC) (419-10 Multifunction Electronic Modules, Removal and Installation).
No REPAIR the circuit.
A7 CHECK THE HORN RELAY CONTROL CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Disconnect BCMC C1035A.
  • Action:
    Positive lead Measurement/Action Negative lead
    C1035A-20 C2280F-20

Is the resistance less than 3 ohms?
Yes GO to A8
No REPAIR the circuit.
A8 CHECK THE BCM-C HORN RELAY CONTROL CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Connect the BCMC C1035A.
  • Connect the battery negative cable.
  • The ignition is on.
  • Action:
    Positive lead Measurement/Action Negative lead
    C2280F-20 Ground

Is the voltage greater than 11 volts?
Yes GO to A17
No CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern, INSTALL a new BCMC.
Refer to: Body Control Module C (BCMC) (419-10 Multifunction Electronic Modules, Removal and Installation).
A9 CHECK THE HORN SUPPLY CIRCUIT
  • Ignition OFF.
  • Disconnect the BCMC C1035B .
  • Disconnect the horn C131.
  • Connect:
    Positive lead Measurement/Action Negative lead
    C131-2 C1035B-60
    C131-1 Ground

Are all resistance measurements less than 3 ohms?
Yes CHECK that fuse 13 (7.5A) is good. If not OK, use the wiring diagrams as a guide to determine the cause of the short circuit. If OK, INSTALL a new horn.
Refer to: Horn (413-06 Horn, Removal and Installation).
No REPAIR the faulty circuit.
A10 CHECK THE HORN SWITCH INPUT AT THE BCM (BODY CONTROL MODULE)
  • Ignition OFF.
  • Disconnect BCM C2280B.
  • With the horn switch pressed, measure:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C2280B-18 Ground

Is the resistance less than 3 ohms?
Yes GO to A17
No GO to A11
A11 DISCONNECT THE HORN SWITCH
  • Connect BCM C2280B.
  • Remove the driver air bag.
    REFER to: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
  • Momentarily connect a fused jumper wire:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C217-1 C217-2

Does the horn sound?
Yes REMOVE the fused jumper wire. INSTALL a new driver air bag module (including the horn switch).
REFER TO: Driver Air Bag Module (501-20B Supplemental Restraint System, Removal and Installation).
No REMOVE the fused jumper wire. GO to A12
A12 CHECK THE HORN SWITCH SIGNAL CIRCUIT
  • Disconnect SCCM C218A.
  • Momentarily connect a fused jumper wire:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C218A-9 Ground

Does the horn sound?
Yes REMOVE the fused jumper wire. GO to A13
No REMOVE the fused jumper wire. REPAIR the open circuit.
A13 CHECK THE HORN SWITCH GROUND FROM THE HORN SWITCH
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217-2 Ground

Is the resistance less than 3 ohms?
Yes GO to A15
No GO to A14
A14 CHECK THE HORN SWITCH GROUND DURING THE SCCM BYPASS
  • Disconnect SCCM C218A.
  • Disconnect the SCCM C218B.
  • Connect a fused jumper wire:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C218A-8 C218B-5
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C217-2 Ground

Is the resistance less than 3 ohms?
Yes REMOVE the fusible link. CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern, INSTALL a new SCCM.
Refer to: Steering Column Control Module (SCCM) (211-05 Steering Wheel and Column Electrical Components, Removal and Installation).
No REMOVE the fused jumper wire. GO to A15
A15 CHECK THE SCCM (STEERING COLUMN CONTROL MODULE) GROUND CIRCUIT FOR AN OPEN
  • Action:
    Click to display the connectors
    Positive lead Measurement/Action Negative lead
    C226A-8 Ground

    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C218A-8 Ground

Is the resistance less than 3 ohms?
Yes INSTALL a new steering wheel (including the steering wheel wiring harness).
Refer to: Steering Wheel (211-04 Steering Column, Removal and Installation).
No REPAIR the circuit.
A16 CHECK THE HORN OPERATION WITH THE STEERING WHEEL WIRING HARNESS DISCONNECTED
  • Disconnect the SCCM C218B.
  • Momentarily connect a fused jumper wire:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    Clockspring C218B, pin 5, component side Ground

Does the horn sound?
Yes REMOVE the fused jumper wire. INSTALL a new steering wheel (including the steering wheel wiring harness).
REFER TO: Steering Wheel (211-04 Steering Column, Removal and Installation).
No REMOVE the fusible link. CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern, INSTALL a new SCCM.
Refer to: Steering Column Control Module (SCCM) (211-05 Steering Wheel and Column Electrical Components, Removal and Installation).
A17 CHECK THE BCM (BODY CONTROL MODULE) OPERATION
  • Disconnect and 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 the horn C131.
  • Reconnect the BCM connectors. Make sure they are fully seated and locked.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern,
Click here to access the guided procedure (BCM). Internet Explorer version 11 or later is required to perform this Pinpoint test.
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.
PINPOINT TEST B: THE HORN IS ALWAYS ON

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

Normal Operation and Fault Symptoms

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

DTC Fault Trigger Conditions

Trouble Code Description Fault Trigger Condition
BCM B1323:11 Horn Switch: Short to Ground Continuous Memory Diagnostic Trouble Code (CMDTC) that is set when the BCM detects a short to ground in the horn circuit.
BCM B1C55:14 Horn Relay: Short to Ground or Open This DTC is set when the BCM detects a short to ground or an open in the horn relay control circuit.

Possible Sources

  • Wiring, Terminals or Connectors
  • Clockspring
  • BCMC
  • Horn Switch
  • BCM
NOTICE: Use the correct probe adapter(s) when making measurements. Using incorrect probe adapter(s) may damage the connector.
NOTICE: The following test uses a test lamp to simulate a normal circuit load. Use only the Rotunda test lamp (SGT27000) or a 250–300 mA incandescent test lamp. To avoid damage to connector terminals, use the Rotunda Flex Probe Kit to connect the test lamp probe to the vehicle. Do not use the test lamp probe directly on any connector.
B1 BCM (BODY CONTROL MODULE) HORN_SW PID (PARAMETER IDENTIFICATION) MONITOR
  • Disconnect the horn C131.
  • The ignition is on.
  • Connect the diagnostic scan tool.
  • Using the diagnostic scan tool, view the BCM (BCM) parameter identification (PID) data.

  • Access the BCM and monitor the HORN_SW PID.


Does the HORN_SW PID status display OFF?
Yes GO to B2
No GO to B4
B2 CHECK THE HORN RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
  • Ignition OFF.
  • Disconnect BCM C2280F.
  • Connect:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C131-1 C131-2

Does the test lamp illuminate?
Yes GO to B3
No GO to B8
B3 DISCONNECT THE HORN RELAY CONTROL CIRCUIT FROM GROUND
  • Ignition OFF.
  • Disconnect the BCM C1035A.
  • Connect:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C1035A-20 Ground

Is the resistance greater than 10000 Ohms?
Yes INSTALL a new BCMC.
REFER TO: Body Control Module C (BCMC) (419-10 Multifunction Electronic Modules, Removal and Installation).
No REPAIR the short to ground in the horn relay control circuit.
B4 ISOLATE THE BCM (BODY CONTROL MODULE) HORN SWITCH INPUT CIRCUIT
  • Ignition OFF.
  • Disconnect BCM C2280B.
  • Connect:
    Click to display connectors
    Positive lead Measurement/Action Negative lead
    C131-1 C131-2

Does the test lamp illuminate?
Yes GO to B8
No GO to B5
B5 CHECK THE HORN SWITCH INPUT CIRCUIT IN THE BCM (BODY CONTROL MODULE) FOR A SHORT TO GROUND
  • Disconnect the clockspring C218A.
  • Connect BCM C2280B.

Does the test lamp illuminate?
Yes REPAIR the circuit.
No GO to B6
B6 DISCONNECT THE HORN SWITCH
  • Remove the driver airbag. Refer to the appropriate section in Group 501.
  • Disconnect the clockspring C218B.
  • Connect the clockspring C218A.

Does the test lamp illuminate?
Yes CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern, INSTALL a new SCCM.
Refer to: Steering Column Control Module (SCCM) (211-05 Steering Wheel and Column Electrical Components, Removal and Installation).
No GO to B7
B7 ISOLATE THE STEERING WHEEL WIRING
  • Connect the clockspring C218B.

Does the test lamp illuminate?
Yes INSTALL a new steering wheel (including the steering wheel wiring harness).
Refer to: Steering Wheel (211-04 Steering Column, Removal and Installation).
No INSTALL a new driver air bag (including the horn switch).
Refer to: Driver Air Bag (501-20B Supplemental Restraint System, Removal and Installation).
B8 CHECK THE BCM (BODY CONTROL MODULE) OPERATION
  • Disconnect and 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
  • Reconnect the BCM connectors. Make sure they are fully seated and locked.
  • Connect the horn C131.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable TSBs, GSBs, SSMs or FSAs. If a service article exists for this concern, STOP this test and FOLLOW the service article instructions. If no service articles apply to this concern,
Click here to access the guided procedure (BCM). Internet Explorer version 11 or later is required to perform this Pinpoint test.
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

A quick Ford Explorer quiz: every answer comes with an explanation and a link to the manual page.