GM Service Manual Online
For 1990-2009 cars only

Radio Circuit Description

Voltage to the radio is available at all times through CKT 1140 (ORN). CKT 1140 provides voltage for radio station memory storage and for the clock memory. With the ignition switch in ACC or RUN, voltage is supplied to the radio through the RADIO (Fuse 17) and CKT 43 (YEL). Each speaker has its own pair of leads. The radio/clock display brightness is at full intensity with the ignition switch in ACC or RUN. The voltage is supplied by CKT 43 (YEL). When the parklamps or headlamps are turned ON, the radio senses the signal and switches voltage for the display from CKT 43 (YEL) to CKT 8 (GRY). Full VFD is achieved by turning the first detent on the headlamp and the parklamp dimmer switch ON. Voltage is supplied to the radio through CKT 1382 (PPL/WHT). The display brightness is then controlled by the Headlamp and Panel Dimmer switch. The radio illumination bulb voltage is supplied by CKT 8 (GRY).

Sub-Woofer Amplifier Circuit Description (Optional)

    • The optional amplifier boosts the sound of the 2 rear speakers when equipped with the premium sound system.
    • With the ignition switch in the ACC or RUN position and the radio control head ON, battery voltage is supplied from the AUX PWR (Fuse 7). Voltage then goes to the sub-woofer amplifier through CKT 840 (ORN).
    • Ground is completed through CKT 1350 (BLK) at the left rear lamps ground G400.

Remote Cassette Tape Player Circuit Description (Optional)

    • With the ignition switch in the RUN position and the radio control head ON, voltage is supplied to the CD player through the radio.
    • With a CD in the remote CD player, the CD player returns a TAPE ON signal.
    • With the remote CD player in PLAY, the stereo audio signals to the radio.
    • The TAPE ON signal causes the receiver circuitry to ignore the signals from the tuner.
    •  The TAPE ON signal sends the studio signals from the tape player to the speakers.
    • When the EJECT button is pushed on the CD player, the TAPE ON signal disappears.
        The radio returns to normal operation.