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Component Tests and General Diagnostics

WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE ATTEMPTING ANY STEERING WHEEL, STEERING COLUMN, OR INSTRUMENT PANEL COMPONENT DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE, THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS IS THE ONLY SURE WAY TO DISABLE THE AIRBAG SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL INJURY.

CAUTION: The speaker output of the audio system uses a "floating ground" design. Do not allow any speaker lead to short to ground, as damage to the radio and/or the amplifier may result.

No Audio
The following tests will confirm that the radio has a ground path and a power supply. These tests should be performed only if the condition noted involves no sound output from all of the audio system speakers.

NOTE: The speaker system and the amplifier (if the vehicle is so equipped) must always be tested and repaired as required before a radio is replaced for a "no audio" condition.

1. Check the Ignition-Off Draw (IOD) fuse (Fuse 16 - 15 ampere) in the Power Distribution Center (PDC). If OK, go to Step 2. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
2. Cheek for battery voltage at the IOD fuse (Fuse 16 - 15 ampere) in the PDC. If OK, go to Step 3. If not OK, repair the open B(+) circuit between the PDC fuse and the battery as required.
3. Check the radio fuse (Fuse 17 - 15 ampere) in the Junction Block (JB). If OK, go to Step 4. If not OK, repair the shorted circuit or component as required and replace the faulty fuse.
4. Turn the ignition switch to the ON position. Check for battery voltage at the radio fuse (Fuse 17 - 15 ampere) in the JB. If OK, go to Step 5. If not OK, repair the open ignition switch output (run-acc) circuit between the JB fuse and the ignition switch as required.
5. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Remove the radio, but do not disconnect the instrument panel wire harness connectors from the radio connector receptacles. Check for continuity between the radio chassis and a good ground. There should be continuity. If OK, go to Step 6. If not OK, repair the open ground circuit to ground (G108) as required.
6. Disconnect the instrument panel wire harness connector (Connector C2 - gray) from the radio connector receptacle. Reconnect the battery negative cable. Check for battery voltage at the fused B(+) circuit cavity of the instrument panel wire harness connector (Connector C2 - gray) for the radio. If OK, go to Step 7. If not OK, repair the open fused B(+) circuit between the radio and the IOD fuse in the PDC as required.
7. Turn the ignition switch to the ON position. Check for battery voltage at the fused ignition switch output (run-acc) circuit cavity of the instrument panel wire harness connector (Connector C2 - gray) for the radio. If OK, replace the faulty radio. If not OK, repair the open fused ignition switch output (run-acc) circuit between the radio and the JB fuse as required.

Vacuum Fluorescent Display
An input to the radio from the headlamp switch through the headlamp switch output circuit allows the radio circuitry to monitor the exterior lighting circuits of the vehicle. The radio circuitry uses this input to provide full intensity illumination of the Vacuum Fluorescent Display (VFD) for improved daylight visibility whenever the exterior lamps are turned OFF. The following test should be used to diagnose a problem where the VFD remains illuminated at full brightness regardless of the headlamp switch position, or a problem where the VFD does not illuminate at full brightness when the headlamp switch is in the OFF position.
1. Disconnect and isolate the battery negative cable. Remove the radio and disconnect the instrument panel wire harness connector (Connector C2 - gray) from the radio connector receptacle. Reconnect the battery negative cable.
2. Turn ON the exterior lamps with the headlamp switch. Check for battery voltage at the headlamp switch output circuit cavity of the instrument panel wire harness connector (Connector C2 - gray) for the radio. If OK, replace the faulty radio. If not OK, repair the open headlamp switch output circuit between the radio and the headlamp switch as required.

Back Lighting
An input to the radio from the headlamp switch through the fused panel lamps dimmer switch signal circuit allows the illumination intensity of the Vacuum Fluorescent Display (VFD) and the incandescent back lighting to be adjusted using the panel dimmer rheostat function of the headlamp switch, whenever the exterior lamps are turned ON. However, this input will not control the illumination intensity of the audio graphic equalizer control LEDs on those radios that are so equipped. As long as the radio power switch is in the ON position, the illumination intensity of these LEDs will remain constant. The following test should be used to diagnose a problem where, while any of the exterior lighting is turned ON, the illumination intensity of the radio VFD and the incandescent back lighting cannot be controlled using the panel dimmer rheostat function of the headlamp switch.

NOTE: If the instrument cluster illumination lamps are also inoperative, be certain to diagnose and repair those lamps before attempting the following test.

1. Disconnect and isolate the battery negative cable. Remove the radio and disconnect the instrument panel wire harness connector (Connector C2 - gray) from the radio connector receptacle. Reconnect the battery negative cable.
2. Turn ON the exterior lamps with the headlamp switch and adjust the panel lamps dimmer rheostat in the headlamp switch to the full bright position. Check for battery voltage at the fused panel lamps dimmer switch signal circuit cavity of the instrument panel wire harness connector (Connector C2 - gray) for the radio. If OK, replace the faulty radio. If not OK, repair the open fused panel lamps dimmer switch signal circuit between the radio and the instrument panel dimmer fuse (Fuse 6 - 5 ampere) in the Junction Block (JB) as required.
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