GM Service Manual Online
For 1990-2009 cars only

Park, Sidemarker, Tail and License Lamps

Voltage is applied continuously to the PARK fuse to the headlamp and the instrument panel (IP) lamp dimmer switch through CKT 1340.

When the headlamp and the (IP) lamp dimmer switch is in the PARK or HEAD position, voltage is applied to CKT 9 thus activating the following lamps:

    • The park lamps
    • The side marker lamps
    • The tail lamps
    • The license lamps

The park/turn lamps are the only lamps that do not activate yet receive a current from CKT 9. The park/turn lamps do not activate because the voltage drop across the front side marker lamps is much higher than that across the turn lamp filaments.

Turn Signal Lamps

When the ignition switch is the in the following positions:

    • The RUN position.
    • The BULB TEST position.
    • The START position.

Voltage is applied through the T/SIG fuse through CKT 539 to the normally closed pole of the turn switch in the turn signal switch assembly, then to the hazard lamp/turn signal flasher through CKT 1508 then back to the turn signal switch through CKT 16.

Voltage is applied from the turn signal switch through CKT 1414 to the DRL control module and then through CKT 14 to the turn filaments of the left front park/turn lamps, when the turn signal switch is the LEFT TURN position. Voltage is also applied through CKT 18 to the left rear turn lamp, the left front side marker and the left turn indicator. The lamps flash ON and OFF as current flow heats up the timing element in the hazard lamp/turn signal flasher, causing it to continuously open and close the circuit. The RIGHT TURN position works in a similar way through CKT 1415 and CKT 19 to the right turn lamps.

Voltage is applied to both terminals of the front side marker lamps causing them to be OFF, when the park lamps and the turn lamps activate. When the turn lamps are not operating, voltage is applied to only 1 terminal of the side marker lamp causing it to flash. The side marker and the turn lamps continue to flash ON and OFF, until the turn switch is turned OFF.

Hazard Lamps

Voltage is applied continuously through the HAZARD fuse through CKT 1840 to the normally open poles of the hazard switch in the turn signal switch assembly.

Voltage is applied to the hazard lamp/turn signal flasher through CKT 1508 then back to the turn signal switch through CKT 16, activating the following lamps to flash ON and OFF:

    • The turn lamps
    • The side marker lamps
    • Both turn indicator lamps

Stop Lamps

Voltage is applied continuously through the STOP LAMP fuse to the stop lamp switch through CKT 140. Depressing the brake pedal applies voltage through the stop lamp switch to CKT 17, thus activating the left and the right stop lamp filaments in the tail/stop lamps and in the center high mounted stop lamp (CHMSL).