GM Service Manual Online
For 1990-2009 cars only

Circuit Operation

Park Marker, Tail and License Lamps

Voltage is applied continuously from the Park LPS fuse to the headlamp switch through circuit 1340. Voltage is applied through circuit 9 when the headlamp switch is in the PARK or the HEAD position.

Current flows through circuit 9 to the following lamps, turning the lamps ON:

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

The only lamps that do not turn ON and receive current from circuit 9 are the turn filaments in the park/turn lamps. The turn filaments in the park/turn lamps do not turn ON because the voltage drop across the front side marker lamps is much greater than that across the turn lamp filaments.

Turn Lamps

Voltage is applied from the turn fuse to the normally closed pole of the turn signal switch through circuit 539, when the ignition switch is in the RUN, BULB TEST or START position. This position feeds the hazard lamp/turn signal lamp flasher through circuit 1508. Voltage is applied from the turn signal switch to circuit 14 at terminal A7 of connector C201 and to circuit 18 at terminal E7 of C201, when the turn signal switch is in the TURN LEFT position.

Voltage is then applied to the following lamps:

    • The left front turn lamp
    • The rear turn lamp
    • The indicator lamps

The lamps flash ON and OFF as current flow heats the timing element in the hazard lamp/turn signal lamp flasher, continuously opening and closing the circuit. For right turn lamps, circuit 15 terminal A6 of C201 and circuit 19 terminal E6 of C201 are used.

When the park lamps and the turn lamps are ON, voltage is applied to both terminals of the front side marker lamp causing the marker lamp to be OFF. Voltage is applied to only 1 terminal of the marker lamp. This causes the marker lamp to flash ON when the front turn lamp is OFF. The turn lamp and the marker lamp continue to flash ON and OFF, out of sequence, until the turn signal switch is turned OFF.

Hazard Lamps

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

Voltage is applied to the following lamps, causing all of the lamps to flash ON and OFF when the hazard switch is in the HAZARD position:

    • The front turn lamps
    • The rear turn lamps
    • The indicator lamps

Stoplamps

Voltage is applied continuously from the STOPLAMP fuse to the stoplamp switch through circuit 140. Voltage is applied from the stoplamp switch to circuit 17 when the brake pedal is pressed.

Voltage is then applied to the turn signal switch, turning ON the following lamps:

    • The left and right stoplamps
    • The center high mounted stoplamp (CHMSL)

Rear Compartment Courtesy Lamp

Voltage is applied continuously from the MALL fuse to the rear compartment courtesy lamp. Ground is applied from G302 through circuit 350 to the rear compartment lid/ajar indicator switch, when the rear compartment is opened. Ground is then applied to the rear compartment courtesy lamp through circuit 744 turning the lamp ON. The lamp turns OFF when the rear compartment is closed.