Horn — 2016 workshop reference 3922

Verify the BJB fuse 21 (20A) is OK.

PINPOINT TEST A : THE HORN IS INOPERATIVE

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). Select the active command BCM HORN_RELAY PID and command the horn ON and then OFF.

Does the horn sound when commanded ON?

Yes	GO to A9
No	GO to A2

A2 CHECK THE HORN RELAY

Ignition OFF. Remove the horn relay and install a known-good relay in its place. Test the horn for normal operation.

Does the horn operate correctly?

Yes	INSTALL a new horn relay.
No	GO to A3

A3 CHECK THE HORN RELAY VOLTAGE SUPPLY CIRCUIT FOR VOLTAGE

Measure:

Positive Lead Measurement / Action Negative Lead Ground Horn relay pin socket 1 Ground Horn relay pin socket 3

Original table alignment retained · Scroll horizontally if needed

Horn — original illustration 1, reference 3922Original colors & callouts · Select to enlarge

Horn — original illustration 2, reference 3922Original colors & callouts · Select to enlarge

Is the voltage greater than 11 volts?

Yes	GO to A4
No	VERIFY BJB fuse 21 (20A) is OK. If OK, REPAIR the horn relay voltage supply circuit. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.

A4 CHECK THE HORN CIRCUITS

Source reference 3922

2016 Mustang workshop publication supplied to Mustang Atlas. Original technical text and illustrations; HTML formatting by Mustang Atlas. Source page numbering is retained for traceability. Follow the configuration, revision, warnings, and cross-references in the material. About this edition.