Horn System: Overview Ford Focus II рестайлинг

Principles of Operation

Note. The smart junction box (SJB) is also known as the generic electronic module (GEM).

The SJB supplies the switched and control voltage to the horn relay (part of the SJB). When the horn switch is pressed, ground is supplied to the SJB through the clockspring. The SJB then energizes the horn relay sending voltage to the horn, enabling the horn to sound.

The horn switch is comprised of the steering wheel and the air bag. They are separated by springs and both have 3 contacts. The steering wheel is the ground and the air bag has a single wire lead. When the driver air bag module is depressed, the springs collapse allowing the contacts to touch, completing the circuit.

The SJB provides a momentary ground to the horn relay when the anti-theft system is armed, and an on then off ground when the panic button is pressed on the remote keyless entry (RKE) key fob.

Normal Operation

The smart junction box (SJB) supplies the switched and control voltage to the horn relay (part of the SJB). When the horn switch is pressed, the switch closes and ground is applied from the steering wheel switch harness through the clockspring to the horn relay through circuit CRH02 (BU/WH). The horn relay is then energized, applying voltage to the horn through circuit CRH04 (VT/GN), enabling the horn to sound. Ground for the horn is supplied through circuit GD164 (BK/VT).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Steering wheel switch harness
4. Horn
5. Clockspring
6. Horn switch
7. SJB

The smart junction box (SJB) supplies the switched and control voltage to the horn relay (part of the SJB). When the horn switch is pressed, the switch closes and ground is applied from the steering wheel switch harness through the clockspring to the horn relay through circuit CRH02 (BU/WH). The horn relay is then energized, applying voltage to the horn through circuit CRH04 (VT/GN), enabling the horn to sound.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Steering wheel switch harness
3. Clockspring
4. Horn switch
5. SJB