Horn System: Overview Ford Taurus VI

Principles of Operation

Note. The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

The SJB supplies the control and switched voltage to the horn relay (integrated into the SJB ). When the horn switch (part of the steering wheel) is pressed, ground is supplied through the clockspring to the horn relay. The horn relay is then energized, directing voltage to the horn and enabling the horn to sound.

The horn switch is comprised 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 air bag module 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.

When the vehicle security system is armed, the SJB provides a momentary ground to the horn relay control side to indicate the system is armed and an on and off ground when an intrusion is detected or the panic alarm is activated.

Normal Operation

The Smart Junction Box (SJB) supplies the switched and control voltage to the horn relay (integrated into the SJB ). When the horn switch (part of the steering wheel) is pressed, ground is supplied to the horn relay, energizing the horn relay. The horn relay then sends voltage to the horn, enabling the horn to sound.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Horn
4. Clockspring
5. Steering wheel harness
6. Horn switch (part of the steering wheel)
7. SJB

The Smart Junction Box (SJB) supplies the switched and control voltage to the horn relay (integrated into the SJB ). When the horn switch (part of the steering wheel) is pressed, ground is supplied to the horn relay, energizing the horn relay. The horn relay then sends voltage to the horn, enabling the horn to sound.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Clockspring
3. Steering wheel harness
4. Horn switches (part of the steering wheel)
5. SJB