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Horn System - Except Electric: Overview Ford Focus III

Horns 2 illustrations ~184 words

Scheme 1

Scheme 1: Horn - Component Location
ItemDescription
1Horn Comments: Located behind lower engine cover

Overview

The horn output is controlled by the Body Control Module (BCM). The Body Control Module (BCM) energizes the horn relay, sounding the horn.

Scheme 2

Scheme 2: System Diagram

Horn Operation

The horn switch consists of 2 sets of contacts separated by springs. The lower set is connected to ground and the upper set is connected to the horn signal circuit. When the driver airbag is pressed, it pushes down on the upper set of contacts, collapsing the springs and allowing the contacts to touch. When the contacts touch, it completes the circuit and provides the ground signal, which is routed through the clockspring to the Body Control Module (BCM). The Body Control Module (BCM) grounds the horn relay coil to energize the relay. When energized, the horn relay provides voltage to the horn, enabling the horn to sound.

Normal Operation and Fault Conditions

Refer to: Horn - System Operation and Component Description .

DTCDescriptionFault Trigger Condition
B1C55:13Horn Relay: Circuit OpenA Continuous Memory Diagnostic Trouble Code (CMDTC) that sets when the BCM detects an open on the horn relay control circuit.
B1C55:19Horn Relay: Circuit Current Above ThresholdA Continuous Memory Diagnostic Trouble Code (CMDTC) that sets when the BCM detects a high current condition on the horn relay control circuit. The BCM disables the horn when this DTC is set.

DTC CHART

Refer to: Horn - System Operation and Component Description .

DTCDescriptionFault Trigger Condition
B1323:11Horn Switch: Circuit Short to GroundA Continuous Memory Diagnostic Trouble Code (CMDTC) that sets when the BCM detects a short to ground on the horn signal circuit.
B1323:23Horn Switch: Signal Stuck LowAn on-demand DTC that sets when the BCM detects a short to ground on the horn signal circuit.
B1C55:11Horn Relay: Circuit Short to GroundA Continuous Memory Diagnostic Trouble Code (CMDTC) that sets when the BCM detects a short to ground on the horn relay control circuit.

DTC CHART