Lincoln Navigator Manuals

Lincoln Navigator: Horn / Horn. Diagnosis and Testing

Lincoln Navigator 2018-2025 Workshop Manual / Instrumentation and Warning Systems / Horn / Horn. Diagnosis and Testing

Diagnostic Trouble Code (DTC) Chart

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices.
REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).


  Diagnostic Trouble Code Chart


Module   DTC Description Action
  BCM B1323:11 Horn Switch:Circuit Short To Ground   GO to Pinpoint Test B
  BCM B1C55:12 Horn Relay:Circuit Short To Battery   GO to Pinpoint Test A
  BCM B1C55:14 Horn Relay:Circuit Short To Ground or Open   GO to Pinpoint Test A

Symptom Chart(s)

Symptom Chart:

Diagnostics in this manual assume a certain skill level and knowledge of Ford-specific diagnostic practices.
REFER to: Diagnostic Methods (100-00 General Information, Description and Operation).

Condition Possible Sources Actions
The horns(s) are inoperative
  • Refer to Pinpoint Test
  • GO to Pinpoint Test A
The horn(s) are always on
  • Refer to Pinpoint Test
  • GO to Pinpoint Test B

Pinpoint Tests


PINPOINT TEST A: THE HORN IS INOPERATIVE

Refer to Wiring Diagrams Cell 44 for schematic and connector information.

Normal Operation and Fault Conditions

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

DTC Fault Trigger Conditions

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

Possible Sources

  • Fuse
  • Wiring, terminals or connectors
  • Clockspring
  • Horn
  • Horn switch
  • BCM
  • BJB

Visual Inspection and Pre-checks

  • Verify the BJB fuse 15 (20A) is OK.

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

A1 CHECK THE BCM (BODY CONTROL MODULE) OUTPUT BY ACTIVATING THE BCM (BODY CONTROL MODULE) HORN_RELAY PID (PARAMETER IDENTIFICATION)
  • Ignition ON.
  • Using a diagnostic scan tool, view BCM Parameter Identifications (PIDs).

  • Access the  BCM  and control the  HORN_RELAY  PID

    and command the horn ON and then OFF.

Does the horn sound when commanded ON?
Yes GO to A11
No GO to A2

A2 CHECK FOR BCM (BODY CONTROL MODULE) DTC (DIAGNOSTIC TROUBLE CODE) B1C55:12, OR B1C55:14
  • Ignition ON.
  • Using a diagnostic scan tool, carry out the BCM 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 HORN RELAY CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
  • Ignition OFF.
  • Disconnect BJB C1035C .
  • Ignition ON.
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C1035C-34   Ground

Is any voltage present?
Yes GO to A4
No GO to A5

A4 ISOLATE THE HORN RELAY VOLTAGE SUPPLY CIRCUIT SHORT TO VOLTAGE
  • Ignition OFF.
  • Disconnect BCM C2280F .
  • Ignition ON.
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C1035C-34   Ground

Is any voltage present?
Yes REPAIR the circuit. TEST system for normal operation.
No GO to A18

A5 CHECK THE HORN RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND
  • Ignition OFF.
  • Disconnect BCM C2280F .
  • Disconnect: negative battery cable.
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C2280F-20   Ground

Is the resistance greater than 10,000 ohms?
Yes GO to A7
No GO to A6

A6 ISOLATE THE HORN RELAY CONTROL CIRCUIT SHORT TO GROUND
  • Disconnect BJB C1035C .
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C2280F-20   Ground

Is the resistance greater than 10,000 ohms?
Yes INSTALL a new BJB .
No REPAIR the circuit. TEST system for normal operation.

A7 CHECK THE HORN RELAY CONTROL CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Disconnect BJB C1035C .
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C1035C-34   C2280F-20

Is the resistance less than 3 ohms?
Yes GO to A8
No REPAIR the circuit. TEST system for normal operation.

A8 CHECK THE BJB INTERNAL HORN RELAY CONTROL CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Connect BJB C1035C.
  • Connect negative battery cable.
  • Ignition ON.
  • Measure:
    Positive Lead Measurement / Action Negative Lead
      C2280F-20   Ground

Is the voltage greater than 11 volts?
Yes GO to A18
No INSTALL a new BJB .

A9 CHECK THE HORN POWER SUPPLY CIRCUIT FOR AN OPEN
  • Ignition OFF.
  • Disconnect BJB C1035A .
  • Disconnect LH Horn C131 .
  • Measure:

      Left hand horn


    Positive Lead Measurement / Action Negative Lead
      C131-2   C1035C-43

Is the resistance less than 3 ohms?
Yes VERIFY BJB BCMC Fuse 15 (20A) is OK. If not OK, use the wiring diagrams as a guide to identify the cause of the circuit short. If OK, INSTALL a new horn.
REFER to: Horn (413-06 Horn, Removal and Installation).
No REPAIR the circuit. TEST the system for normal operation. If the horn is still inoperative, GO to A10

A10 CHECK THE HORN GROUND CIRCUIT
  • Measure:

      Left hand horn


    Positive Lead Measurement / Action Negative Lead
      C131-1   Ground

Is the resistance less than 3 ohms?
Yes VERIFY BJB Fuse 15 (20A) is OK. If not OK, use the wiring diagrams as a guide to identify the cause of the circuit short. If OK, INSTALL a new horn.
REFER to: Horn (413-06 Horn, Removal and Installation).
No REPAIR the circuit. TEST system for normal operation.

A11 CHECK THE HORN SWITCH INPUT TO THE BCM (BODY CONTROL MODULE)
  • Ignition OFF.
  • Disconnect BCM C2280B
  • While pressing the horn, measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C2280B-18   Ground

Is the resistance less than 3 ohms?
Yes GO to A18
No GO to A12

A12 ISOLATE THE HORN SWITCH
  • Connect BCM C2280B
  • Remove the driver airbag.
    REFER to: Driver Airbag (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 airbag (includes horn switch).
REFER to: Driver Airbag (501-20B Supplemental Restraint System, Removal and Installation).
No REMOVE the fused jumper wire. GO to A13

A13 CHECK THE HORN SWITCH SIGNAL CIRCUIT
  • Disconnect SCCM C226A.
  • 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 A14
No REMOVE the fused jumper wire. REPAIR the open circuit.

A14 CHECK THE HORN SWITCH GROUND FROM THE HORN SWITCH
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C217-2   Ground

Is the resistance less than 3 ohms?
Yes GO to A17
No GO to A15

A15 CHECK THE HORN SWITCH GROUND WHILE BYPASSING THE SCCM (STEERING COLUMN CONTROL MODULE)
  • Disconnect SCCM C226A.
  • Disconnect Clockspring C218B.
  • Connect a fused jumper wire:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C226A-8   C218B-4
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C217-2   Ground

Is the resistance less than 3 ohms?
Yes REMOVE the fused jumper wire. CHECK OASIS for any applicable TSB , GSB , SSM , or FSA . If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address 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 A16

A16 CHECK THE SCCM (STEERING COLUMN CONTROL MODULE) HORN GROUND CIRCUIT FOR AN OPEN
  • Measure:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C226A-8   Ground

Is the resistance less than 3 ohms?
Yes INSTALL a new steering wheel (includes steering wheel wiring harness).
REFER to: Steering Wheel (211-04 Steering Column, Removal and Installation).
No REPAIR the circuit.

A17 CHECK HORN OPERATION WITH STEERING WHEEL HARNESS ISOLATED
  • Disconnect 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 (includes steering wheel wiring harness).
REFER to: Steering Wheel (211-04 Steering Column, Removal and Installation).
No REMOVE the fused jumper wire. CHECK OASIS for any applicable TSB , GSB , SSM , or FSA . If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new SCCM .
REFER to: Steering Column Control Module (SCCM) (211-05 Steering Wheel and Column Electrical Components, Removal and Installation).

A18 CHECK FOR CORRECT 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
    • pushed-out pins – install new pins as necessary
  • Connect LH Horn C131
  • Reconnect the BCM connectors. Make sure they seat and latch correctly.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB , GSB , SSM , or FSA . If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new BCM
REFER to: Body Control Module (BCM) (419-10 Multifunction Electronic Modules, Removal and Installation).
No The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.

PINPOINT TEST B: THE HORN IS ALWAYS ON

Refer to Wiring Diagrams Cell 44 for schematic and connector information.

Normal Operation and Fault Conditions

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

DTC Fault Trigger Conditions

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

Possible Sources

  • Wiring, terminals or connectors
  • Clockspring
  • Horn switch
  • BCM
  • BJB

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTICE: The following test uses a test light to simulate normal circuit loads. Use only a Rotunda Test Lamp (SGT27000) or 250-300mA incandescent bulb test lamp. To avoid connector terminal damage, use the Rotunda Flex Probe kit for the test lamp probe connection to the vehicle. Do not use the test lamp probe directly on any connector.

B1 MONITOR THE BCM (BODY CONTROL MODULE) HORN_SW PID (PARAMETER IDENTIFICATION)
  • Disconnect LH Horn C1101
  • Ignition ON.
  • Connect a diagnostic scan tool.
  • Using a diagnostic scan tool, view BCM Paramater Identifications (PIDs).

  • Access the  BCM  and monitor the  HORN_SW  PID


Does the 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
      C131-2   C131-1

Does the test light illuminate?
Yes GO to B3
No GO to B8

B3 ISOLATE THE HORN RELAY CONTROL CIRCUIT SHORT TO GROUND
  • Ignition OFF.
  • Disconnect BJB C1035C
  • Connect:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C1035C-34   Ground

Is the resistance greater than 10,000 ohms?
Yes INSTALL a new BJB .
No REPAIR the circuit. TEST system for normal operation.

B4 ISOLATE THE BCM (BODY CONTROL MODULE) HORN SWITCH INPUT CIRCUIT
  • Ignition OFF.
  • Disconnect BCM C2280F
  • Connect:
    Click to display connectors
    Positive Lead Measurement / Action Negative Lead
      C131-2   C131-1

Does the test light illuminate?
Yes GO to B8
No GO to B5

B5 CHECK THE HORN SWITCH INPUT CIRCUIT TO THE BCM (BODY CONTROL MODULE) FOR A SHORT TO GROUND
  • Disconnect SCCM C226A
  • Connect BCM C2280B

Does the test light illuminate?
Yes REPAIR the circuit. TEST the system for normal operation.
No GO to B6

B6 ISOLATE THE HORN SWITCH
  • Remove the driver airbag.
    REFER to: Driver Airbag (501-20B Supplemental Restraint System, Removal and Installation).
  • Disconnect Clockspring C218A
  • Connect SCCM C226A

Does the test light illuminate?
Yes INSTALL a new clockspring.
REFER to: Clockspring (501-20B Supplemental Restraint System, Removal and Installation). TEST the system for normal operation. If the test light remains illuminated, 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 Clockspring C218C

Does the test light illuminate?
Yes INSTALL a new steering wheel (includes steering wheel wiring harness).
REFER to: Steering Wheel (211-04 Steering Column, Removal and Installation).
No INSTALL a new driver airbag (includes horn switch).
REFER to: Driver Airbag (501-20B Supplemental Restraint System, Removal and Installation).

B8 CHECK FOR CORRECT 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
    • pushed-out pins – install new pins as necessary
  • Connect LH Horn C131
  • Reconnect the BCM connectors. Make sure they seat and latch correctly.
  • Operate the system and determine if the concern is still present.

Is the concern still present?
Yes CHECK OASIS for any applicable service articles: TSB , GSB , SSM , or FSA . If a service article exists for this concern, DISCONTINUE this test and FOLLOW the service article instructions. If no service articles address this concern, INSTALL a new BCM
REFER to: Body Control Module (BCM) (419-10 Multifunction Electronic Modules, Removal and Installation).
No The system is operating correctly at this time. The concern may have been caused by module connections. ADDRESS the root cause of any connector or pin issues.


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