Description Of Operation

WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Communication Flow - Rear Fog Light

Courtesy of SAAB-SCANIA OF AMERICA, INC.

Fig 2: Identifying Rear Fog Light Circuit Diagram

Courtesy of SAAB-SCANIA OF AMERICA, INC.

The rear fog light is turned on with the rear fog light switch. The rear fog light must be reactivated each time the ignition is switched on. The rear fog light can be turned on when the light switch is in position 1 or 2 and the ignition switch is in the ON position.

So that DICE can safely determine in which position (0-1-2) the switch (10) is, it uses information from TWICE and its own pin connection.

The parking lights are controlled by TWICE which gives information to the bus (ON/OFF). The message ON corresponds to switch position 1 and the message OFF corresponds to switch positions 1 or 2.

DICE pin 39 is connected to switch pin 5, which corresponds to position 0. DICE pin 15 is connected to switch pin 4, which corresponds to position 2.

Voltage +15 is fed to the rear fog light via DICE (628). When switch (161) is pushed in, voltage +15 is fed via fuse 19 to pin 16 on the control module. The lamp (33 HL alt. 33 HR) is then powered from DICE pin 25.

DICE sends information about the status of the rear fog light (ON/OFF). This is used by MIU (main instrument unit) to turn the indicator lamp for the rear fog light on or off.

Pin 25 on DICE is intended for a trailer connector (258).

To prevent unnecessary loading on the battery when the starter motor is activated, DICE turns the rear fog light off. When the ignition switch returns to ON from the ST position, DICE turns the rear fog light on again. The off period is limited to 20 seconds for safety reasons, so that the rear fog light will function even in the event of a fault, i.e. if there is no +54 voltage.