GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Body and Accessories 🢒 Entertainment 🢒 Radio/Audio System Description and Operation

The Radio/Audio System consists of 2 levels of audio entertainment:

    • Base Level
    • Uplevel

Both levels of audio entertainment contain a speaker system that is appropriate for each radio/audio level and a choice of radios that contain various options.

Radio/Audio System Content

Base Level Audio System

Uplevel Audio System

UM7 Radio with AM/FM Stereo

UM6 Radio with AM/FM Stereo and Auto-Reverse Cassette

UL0/UP0 Radio with AM/FM Stereo and Auto-Reverse Cassette. UP0 includes a single CD Remote Playback Device

UN0 Radio with AM/FM Stereo and CD Player

Fixed Mast Antenna

Fixed Mast Antenna

Fixed Mast Antenna

Fixed Mast Antenna

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Optional Remote Playback Device- CD Changer

Optional Remote Playback Device- CD Changer

Playing the Radio (Base Level)

VOLUME-BAL

    • The ignition switch must be in the ACCESSORY or RUN position to operate the radio.
    • The radio power switch is integral with the volume control.
    • Use the radio power switch/volume control knob in order to turn the system ON and OFF and to control the volume.
    •  Turn the radio power switch clockwise in order to turn the system ON or to increase the volume.
    • Turn the radio power switch counterclockwise in order to turn the system OFF or to decrease the volume.

RECALL

    • The RECALL function can only be performed with the radio ON.
    • Press the volume control knob to toggle the display between the time of day or the radio frequency.
    • Press the volume control knob to briefly display the time of day while the radio is turned OFF.

Finding a Station (Base Level)

AM-FM

Press the tune knob in order to change the radio band between AM and FM. The display will indicate the current band and the last radio frequency that was selected on that band.

TUNE

    • Rotate the TUNE knob clockwise in order to increase the AM or FM frequency.
    • Rotate the TUNE knob counterclockwise in order to decrease the AM or FM frequency.

SEEK

    • Press the right arrow button in order to tune into the next station higher in frequency.
    • Press the left arrow button in order to tune into the next station lower in frequency.

SCAN

  1. Press both SEEK buttons in order to activate the SCAN mode.
  2. SCAN will appear on the display and the radio will stop at every station for a few seconds.
  3. Press the right arrow button in order to tune into the next higher station
  4. Press the left arrow button in order to tune into the next lower station.
  5. Press VOLUME or both SEEK buttons to stop scanning.

PUSH BUTTONS

Up to 14 stations can be preset into the radio's memory using the numbered push buttons (1,3,5, and 7). In order to preset 4 AM and 4 FM stations, perform the following steps:

  1. Tune to the desired radio station.
  2. Press the SET push button. SET will appear on the display.
  3. Press and hold a numbered push button until the SET display goes off. The radio will tune to the preset station the next time the same push button is pressed.

In order to preset 3 additional AM and 3 additional FM stations perform the following steps:

  1. Tune to the desired radio station.
  2. Press the SET push button. SET will appear on the display.
  3. Press and hold two adjacent push buttons (1 and 3) until the SET display goes off. The radio will tune to the preset station the next time both push buttons are pressed.
  4. Repeat the first 2 steps for each remaining pair of push buttons (3 and 5, or 5 and 7).

Setting the Tone (Base Level)

BASS

    • Slide the BASS lever up in order to increase the bass response.
    • Adjust the BASS lever down in order to decrease the bass response.

TREB

    •  Slide the TREB level up in order to increase the treble response.
    • Slide the TREB lever down in order to reduce the noise if the station is weak or noisy.

Adjusting the Speakers (Base Level)

BAL

    • Turn the BAL control knob behind the VOLUME knob to select more or less sound, distributed between the left or the right speakers.
    • The middle position will deliver an equal balance of sound between the left and right speakers.

FADE

    • Turn the FADE control knob behind the TUNE knob to select more or less sound, distributed between the front and rear speakers.
    • The middle position will deliver an equal balance of sound between the front and rear speakers.

Playing a Cassette Tape (Base Level)
  1. In order to play a tape, the ignition switch must be in the ACCESSORY or RUN position and the receiver must be turned ON.

    2. Tapes are end-loaded into the cassette player.

  2. Insert the tape squarely through the door, exposed tape side of the cassette facing to the right.
  3. When the tape is fully inserted, the AM/FM portion of the radio will turn off and the tape will begin playing.
  4. The tape player works best with tapes that are 30-45 minutes long on each side.

    5. Longer running tapes may not work well in these players because they are usually too thin.

  5. Once the tape is playing, the volume, balance and fade knobs operate the same as with the radio.

    6. An arrow indicates which side of the tape is being played.

FWD

  1. Press the SEEK right arrow key in order to fast forward the tape.
  2. Press the SEEK left arrow key in order to stop the fast forward operation.

REV

  1. Press the SEEK left arrow key in order to rewind the tape.
  2. Press the SEEK right arrow key in order to stop rewinding the tape.

RECALL

Press the volume control knob to change from one side of the tape to the other.

EJECT

Press the EJECT push button in order to remove the tape or in order to stop the tape and switch to the radio.

CLN

  1. If CLN appears on the display, the cassette player needs to be cleaned in order to prevent damage to the tape player.
  2. After cleaning the tape player, press and hold the EJECT button for 5 seconds in order to reset the CLN indicator.
  3. The radio displays "- - -" in order to show that the indicator has been reset.

Playing the Radio (Uplevel)

PWR-VOL

    • Push the PWR-VOL knob in order to turn the radio ON and OFF.
    • Rotate the volume control clockwise in order to increase the volume.
    • Rotate the volume control counterclockwise in order to decrease the volume.

RECALL

    • The RECALL function can only be performed with the radio ON.
    • Press the RECALL push button to toggle the display between the time of day or the radio frequency.
    • Press the RECALL push button to briefly display the time of day while the radio is turned OFF.

Speed Compensated Volume (SCV)

    • In order to use the SCV, adjust the volume to the listening level you want and move the control ring behind the PWR-VOL knob to adjust the SCV.
    • The volume level automatically adjusts to compensate for road and wind noise as you drive.
    •  As you drive, the volume level will change in order to compensate for the noise present at any particular speed.
    • Each detente on the SCV allows for more compensation at a faster rate.

Finding a Station (Uplevel)

AM-FM

    • Press the AM/FM push-button to switch between AM, FM1, and FM2.
    • The display indicates the current band.

TUNE

  1. Press lightly on the TUNE control in order to release the tune control from the tune control's recessed position.
  2. Rotate the TUNE knob to the right in order to increase the frequency.
  3. Rotate the TUNE knob to the left in order to decrease the frequency.
  4. Push the TUNE control back in order to store the frequency setting while not tuning.

SEEK

    • Press the right arrow key in order to tune into the next higher frequency.
    • Press the left arrow key in order to tune into the next lower frequency.
        Audio is muted during the SEEK operation.

SCAN

  1. Press and hold SEEK for 2 seconds. SCAN will appear on the display.
  2. Use SCAN in order to listen to each radio station for a few seconds.
  3. Press SEEK again in order to stop scanning.

PUSH BUTTONS

Up to 18 stations (6 AM, 6 FM1, and 6 FM2) can be preset into the radio's memory using the 6 numbered push buttons. In order to preset a station in memory, perform the following steps:

  1. Press AM-FM in order to select the band.
  2. Tune to the desired station, using the TUNE knob or SEEK.
  3. Press AUTO TONE in order to select the setting that you prefer.
  4. Press and hold 1 of the 6 push buttons until audio returns (approximately 2 seconds).
  5. Whenever you press that push button, the preset station will return.

    6. The AUTO TONE that you selected will also be automatically selected for that push button.

PSCAN

Any stations already stored in preset memory can be sampled by the PSCAN mode.

  1. In order to use PSCAN, press the PSCAN push button.

    2. PSCAN will scan each of the presets and stop for a few seconds.

  2. Press PSCAN or another push-button in order to stop scanning to listen to a specific station.

    3. PSCAN appears in the display whenever the tuner is in the PSCAN mode.

    If 1 of the stations stored on a push-button is weak, the radio display shows the channel number (P1-P6) for several seconds before advancing to the next preset station.

Setting the Tone (Uplevel)

AUTO TONE

The automatic tone control (ATC) feature tailors the equalization to the type of broadcast being received.

  1. Press AUTO TONE in order to step through the 6 preset equalization settings of CLASSIC, NEWS, ROCK, POP, JAZZ, or C/W (Country Western).

    2. Note the graph and words in the display for each press of the push button.

  2. One or more presses of the AUTO TONE push-button brings up manual (MAN) and return the control of tone back to the TREB and BASS controls.
  3. Any time that a BASS or TREBLE control rotates, the tone automatically sets to MAN.

BASS

  1. Depress the BASS control in order to remove the control from the recessed position.
  2. Rotate the BASS control to the right in order to increase the bass response.
  3. Rotate the BASS control to the left in order to decrease the bass response.
  4. Operation of this control will switch the radio's AUTO TONE feature to MAN.
  5. Push the control knob back in to store when not in use.

TREBLE

  1. Depress the TREB control in order to remove the control from the recessed position.
  2. Pull the TREB control out to a fully extended position in order to make TREB adjustments.
  3. Rotate the TREB control to the right in order to increase the treble response.
  4. Rotate the TREB control to the left in order to decrease the treble response.
  5. Operation of this control will switch the radio's AUTO TONE feature to MAN.
  6. Push the control knob back in to store when not in use.

Adjusting the Speakers (Uplevel)

BALANCE

  1. Depress the BAL control in order to remove the control from the recessed position.
  2. Rotate the balance to the right in order to adjust the sound to the right speakers.
  3. Rotate the balance to the left in order to adjust the sound to the left speakers.
  4. Push the control knob back in to store when not in use.

FADE

  1. Depress the FADE control in order to remove the control from the recessed position.
  2. Rotate the FADE control knob to the right in order to adjust the sound to the front speakers.
  3. Rotate the FADE control knob to the left in order to adjust the sound to the rear speakers.
  4. Push the control knob back in order to store when not in use.

Playing a Cassette Tape (Uplevel)
  1. Tapes may be played with the ignition ON or OFF.

    2. If the ignition is ON but the radio is OFF, the tape will begin playing.

    A tape symbol, accompanied by tape direction arrows, is shown in the center of the graphic display whenever a tape is playing.

  2. Tapes are end-loaded into these players. Insert the tape squarely through the door, exposed tape side of the cassette facing the right.
  3. When the tape is fully inserted, the AM/FM portion of the radio will turn OFF and the tape will begin playing.
  4. The tape player works best with tapes that are 30 to 45 minutes long on each side. Longer tapes may not work well in the cassette player because the tapes are so thin.
  5. To load a cassette with the ignition in the OFF position, press EJECT or RECALL.
  6. Insert the cassette.
  7. If the ignition is in the ON position and the radio is in the OFF position, the tape will begin to play.
  8. The player automatically senses the tape cartridge for metal or Cr02 tape media and presets the pre-emphasis.

    9. For metal tapes, "DD" will be displayed.

  9. Any time a tape is playing, use the volume, balance, fade, treble, and bass just as with the radio.

    10. An arrow indicates which side of the tape is being played.

  10. When you insert a tape, the top of the cassette plays first.

PREV

    • Press the PREV or the SEEK left arrow push button in order to search for the previous selection.
        The tape direction arrow blinks during SEEK operation.
    •  A minimum 3 second blank gap is required for proper operation.
    • Audio is muted during SEEK.

PROG

Press the PROG push button in order to switch from one side of the tape to the other.

NEXT

    • Press the NEXT or the SEEK right arrow push button in order to search for the next selection.
    • A minimum of a 3 second gap is required for the player to stop at the beginning of a selection.
    • The tape direction arrow will blink during the SEEK operation.

REV

    • Press REV in order to rewind the tape. The tape rapidly reverses to the beginning of the cassette or until you press the REV push-button a second time.
        The radio plays the last selected station during the REV operation.
    • The tape direction arrow blinks during REV operation.

DOLBY®

Dolby Noise Reduction is manufactured under a license from Dolby Laboratories Licensing Corporation. Dolby® and the "DD" symbol are trademarks of Dolby Laboratories Licensing Corporation.

  1. Press the Dolby push-button in order to reduce cassette tape noise.
  2. The "DD" Dolby® symbol will appear in the display.

FWD

  1. Press FWD in order to fast-forward the tape. The tape rapidly advances to the end of the tape or until you press the FWD push-button again.
  2. The radio will play the last selected station during the FWD operation.
  3. The tape direction arrow blinks during FWD operation.

AM-FM

Press the AM-FM button in order to switch from tape to radio.

TAPE AUX

  1. Press TAPE AUX in order to return to the tape player.
  2. The lighted arrow appears and shows the direction of play when a tape is in the active mode.

EJECT

  1. In order to remove the tape, press EJECT.
  2. EJECT may be activated with either the ignition or the radio OFF.
  3. Cassettes may be loaded with the radio OFF by pressing EJECT before loading the cassette tape.

CLN

  1. If CLN appears on the display, the cassette player needs to be cleaned in order to prevent damage to the tape player.
  2. After cleaning the tape player, press and hold EJECT for 5 seconds in order to reset the CLN indicator.
  3. The radio displays "- - -" in order to show that the indicator reset.

Playing a Compact Disc (Uplevel)

PWR

  1. Press the PWR knob in order to turn the system on.
  2. The system can be turned on by inserting a compact disc into the player with the ignition in the ON position.
  3. Insert a disc partway into the slot, label side up.
  4. The player pulls the disc in.
  5. When inserted, the disc will begin playing track 1.
  6. Wait a few seconds until the disc plays.
  7. The letters "CD" and a CD symbol appears on the display.
  8. If the disc comes back out and ERR appears on the display, inspect for the following conditions:
    9. • The disc is upside down.
    • The disc is dirty, scratched, or wet.
    • There is too much moisture in the air.
    • Wait an hour and try again.
    • The vehicle is operating on a very rough road.
    • The disc player is very hot.
  9. Press RECALL in order to eliminate the ERR message.

RECALL

  1. Press the RECALL button in order to see what track is playing.
  2. Press the RECALL button again within 5 seconds in order to see the elapsed time of the current track.
  3. The track number appears when a new track begins to play.
  4. Press RECALL again in order to return to the time display.

PREV

  1. Press PREV or the SEEK left arrow in order to search for the previous selection.
  2. If you hold the PREV button or press it more than once, the disc advances further.

RDM

  1. The random playback (RDM) feature allows the tracks on the compact disc to be played in random order rather than in sequential order.
  2. During random playback, a RANDOM indicator appears in the display.
  3. Press RDM again in order to return to normal play.

NEXT

  1. Press NEXT or the SEEK right arrow in order to search for the next selection.
  2. If you hold the NEXT button or press it more than once, the disc will advance further.
  3. The next track number will appears on the display.

REV

  1. Press and hold the REV button in order to quickly reverse within a track.
  2. When the CD reverses, elapsed time displays in order to find the correct passage.

FWD

  1. Press and hold the FWD button in order to quickly advance within a track.
  2. When the CD advances, elapsed time displays in order to find the correct passage.

AM-FM

  1. While in the CD mode, press the AM-FM button in order to stop playing the CD and play the radio.
  2. The CD symbol will still be displayed but the letters CD are replaced with AM, FM1, or FM2.
  3. If the radio is turned OFF, the disc will remain in the player and resume playing at the point where it stopped, when the radio is turned ON.

CD AUX

  1. Press the CD AUX button in order to return from listening to the radio and play the CD.
  2. When a disc plays, the letters "CD" and the CD symbol will appear on the display.
  3. If the radio is turned OFF, the disc will remain in the player and resume playing at the point where it stopped, when the radio is turned ON.

EJECT

    • Press EJECT in order to eject the disc from the CD player.
    • A disc that has been ejected but not removed from the player will be pulled back in within 30 seconds.
    • This protects the disc and the player from damage.
    • The disc does not play.
    • In order to remove the disc, press the EJECT button and remove the disc from the player.

Remote Playback Device-- CD Player (Uplevel)

In order to operate the Compact Disc player, perform the following steps:

  1. Insert a disk part way into the slot, label side up.
  2. If the radio is in the OFF position and the ignition is in the ON position when you insert the CD, the radio turns on and begins playing the CD.
  3. In order to load a CD with the ignition in the OFF position, press the EJECT button on the remote player and insert the disc.
  4. In order to remove the disc, press the EJECT button and remove the disc.
  5. All of the compact disc functions are controlled by the radio buttons except EJECT.
  6. When a disc is in the player, a CD symbol appears next to the CD symbol in the bottom left corner on the display.

    7. The track number will also be displayed .

  7. If the disc comes back out and ERR appears on the display, inspect for the following conditions:
    8. • An upside down disc
    • A dirty, scratched, or wet disc
    • Too much moisture in the air
    • If there is too much moisture in the air, wait about 1 hour and try again.
    • The vehicle is operating on a very rough road.

TAPE AUX

  1. With a disc loaded in the player and the radio playing, press the TAPE AUX button once in order to play the compact disc.
  2. Press AM-FM in order to return to the radio.
  3. If you load both a cassette and a CD, press TAPE AUX in order to switch between the tape and the compact disc.

SEEK

  1. Press the left arrow while playing a CD in order to go back to the beginning of the current track.
  2. The CD goes back to the current track if more than 8 seconds have played.
  3. Press the left arrow again in order to go to the previous tracks.
  4. Press the right arrow in order to go to the next higher track on the disc.

PREV

  1. Press PREV in order to go back to the beginning of a current track.
  2. The CD goes back to the current track after 8 seconds have played.
  3. Press PREV again in order to go the previous track on the disc.

PROG

The PROG button functions only when the vehicle is equipped with a 12-disc changer.

NEXT

Press the NEXT button in order to advance to the next track on the disc.

REV

  1. Press and hold the REV button in order to quickly reverse within a track.
  2. When the CD reverses, elapsed time displays in order to find the correct passage.

FWD

  1. Press and hold the FWD button in order to advance within a track.
  2. When the CD advances, elapsed time displays in order to find the correct passage.

RANDOM

  1. Press PSCAN in order to enter the RANDOM play mode.

    2. RANDOM will appear on the display.

  2. While in this mode, the tracks on the disc will be played in random order.
  3. If you press the SEEK, PREV, or NEXT buttons while in the random mode, the PREV or NEXT track scans randomly.
  4. Press PSCAN again in order to turn off RANDOM and return to normal operation.

EJECT

    • Press EJECT in order to eject the disc from the CD player.
    • A disc that has been ejected but not removed from the player will be pulled back in within 30 seconds.
        This protects the disc and the player from damage.
    • The disc does not play.
    • In order to remove the disc, press the EJECT button and remove the disc from the player.

RECALL

  1. Press RECALL in order to see what track is playing.
  2. Press RECALL again within 5 seconds in order to view elapsed time.
  3. Press RECALL a third time and the time of day will be displayed.

Theftlock™ (Uplevel)

Important: Read all steps before starting the procedure.

If more than 15 seconds elapse between any of the steps, the radio automatically reverts to time and you must start the procedure over from step 4.

If SEC appears on the display in step 4, the system has already been activated.

To change the code, the old code must be removed first.

In order to activate the Theftlock™ system, perform the following steps:

  1. Write down any number from 000 to 1999.
  2. Turn the ignition to the ACCESSORY or the RUN position.
  3. Turn the radio OFF.
  4. Press the 1 and 4 push-buttons together. Hold them down until "- - -"shows on the display.
  5. Press MN and 000 will appear on the display.
  6. Press and hold MN again until the last two digits agree with your code.
  7. Press and hold HR to make the first 1 or 2 digits agree with your code.
  8. Press the AM/FM push button after you have confirmed that the code matches the code you wrote down. If REP appears on the display, repeat steps 5 through 8.
  9. SEC will appear on the display, the radio is now operable and secured.
  10. With the ignition OFF, the Theftlock™ indicator flashes.

Activating the Theftlock™ Feature

Important: Read all steps before starting the procedure.

If more than 15 seconds elapse between any of the steps, the radio automatically reverts to time and you must start the procedure over from step 4.

If SEC appears on the display in step 4, the system has already been activated.

To change the code, the old code must be removed first.

In order to activate the Theftlock™ system, perform the following steps:

  1. Write down any number from 000 to 1999.
  2. Turn the ignition to the ACCESSORY or the RUN position.
  3. Turn the radio OFF.
  4. Press the 1 and 4 push-buttons together. Hold them down until "- - -"shows on the display.
  5. Press MN and 000 will appear on the display.
  6. Press and hold MN again until the last two digits agree with your code.
  7. Press and hold HR to make the first one or two digits agree with your code.
  8. Press the AM/FM push button after you have confirmed that the code matches the code you wrote down. If REP appears on the display, repeat steps 5 through 8.
  9. SEC will appear on the display, the radio is now operable and secured.
  10. With the ignition OFF, the Theftlock™ indicator flashes.

Unlocking a Radio That Displays LOC When Code is Known

Important: Read all steps before starting the procedure.

If more than 15 seconds elapse between any of the steps, the radio automatically reverts to time and you must start the procedure over from step 4.

In order to unlock the Theftlock™ system after a power loss, perform the following steps:

  1. Write down the users code.
  2. Turn the ignition to the RUN position.
  3. Press MN and 000 will appear on the display.
  4. Press and hold MN until the last two digits agree with the code.
  5. Press and hold HR until the first one or two digits agree with the code.
  6. Press the AM/FM push button after you have confirmed that the code matches the one you wrote down. If REP appears on the display, repeat steps 3 through 6.
  7. SEC will appear on the display, the radio is now operable and secured.

If the wrong code is entered more than eight times, INOP will appear on the display.

Wait 1 hour before attempting to unlock the radio again.

This time only 3 attempts will be allowed before INOP appears on the display.

If this happens you must wait 1 hour before attempting to unlock the radio again.

Unlocking a Radio That Displays LOC When Code is Unknown

Important: Starting in 1995, a factory back-up code can be used to erase the original code if it is unknown.

Have account number ready to enter when asked. Account number is your 5 digit dealer code followed by one of these numbers:

   • Chevrolet - 1
   • Pontiac - 2
   • Oldsmobile - 3
   • Buick - 4
   • GMT - 5
   • Cadillac - 6
   • GM Canada - 7
   • Saturn - 8
Read all steps before starting the procedure.

If more than 15 seconds elapse between any of the steps, the radio automatically reverts to time and you must start the procedure over from step 1.

In order to unlock the Theftlock™ system when code is unknown, perform the following steps:

  1. Press and hold push buttons 2 and 3 until a three digit code appears on the display.
  2. Write the three digit code on a piece of paper.
  3. Press the AM/FM push button, a three digit code will appear on the display again.
  4. Write the three digit code on a piece of paper.
  5. Call Delco Electronics at 1- 800 - 537 - 5140.
  6. Follow the computer prompts to obtain the back-up code to be used in place of unknown code.
  7. Press MN and 000 will appear on the display.
  8. Press and hold MN until the last two digits agree with the back-up code.
  9. Press and hold HR until the first one or two digits agree with the back-up code.
  10. Press the AM/FM push button after you have confirmed that the code matches the one you wrote down. If REP appears on the display, repeat steps 7 through 10.
  11. The display will show "- - -" to indicate unknown code has been removed.

If the back-up code does not unlock the radio, try reversing the first and last three digits of the display code.

If this is unsuccessful, call Delco Electronics to obtain a new factory back-up code.

Disabling the Theftlock™ Feature

Important: If more than 15 seconds elapse between any of the steps, the radio automatically reverts to time and you must start the procedure over from step 3.

In order to disable the Theftlock™ feature, enter the user code as follows:

  1. Turn the ignition to ACCESSORY or RUN.
  2. Turn the radio OFF.
  3. Press the 1 and 4 buttons together. Hold then down until SEC appears on the display.
  4. Press MN and "000" will appear on the display.
  5. Press and hold MN until the last two digits agree with the user code.
  6. Press and hold HR until the first one or two digits agree with the user code.
  7. Press the AM/FM push button after you have confirmed that the code matches the one you wrote down. If REP appears on the display, repeat steps 4 through 7.
  8. The display will show "- - -", indicating that the radio is no longer secured.
  9. If the code is entered incorrectly, SEC appears on the display.
  10. The radio will remain secured until the correct code is entered.