Several combinations of radio receivers and speaker systems are offered on this model. The audio system uses an ignition switched source of battery current so that the system will only operate when the ignition switch is in the RUN or ACCESSORY positions.
The audio system includes the following components
- Antenna
- Power amplifier
- Radio noise suppression components
- Radio receiver
- Remote radio switches (if equipped)
- Speakers
- Subwoofer
Certain functions and features of the audio system rely upon resources shared with other electronic modules in the vehicle over the Controlled Area Network (CAN). The data bus network allows the sharing of sensor information. For diagnosis of these electronic modules or of the data bus network, the use of a scan tool and the proper Diagnostic Procedures information is recommended.
OPERATION
The audio system components are designed to provide audio entertainment and information through the reception, tuning and amplification of locally broadcast radio signals in both the Amplitude Modulating (AM) and Frequency Modulating (FM) commercial frequency ranges.
The audio system components operate on battery current received through a fuse in the Totally Integrated Power Module (TIPM) on a fused ignition switch output (RUN-ACC) circuit so that the system will only operate when the ignition switch is in the Run or Accessory positions.
On vehicles that are equipped with the optional remote radio switches, the Cab Compartment Node (CCN) receives hard wired resistor multiplexed inputs from the remote radio switches. The programming in the CCN allows it to process those inputs and send the proper messages to the radio receiver over the Controlled Area Network (CAN) to control the radio volume up or down, station seek up or down, preset station advance, and mode advance functions.
Refer to the owner's manual for more information on the features, use and operation of each of the available audio systems.
Any diagnosis of the Audio system should begin with the use of scan tool. For information on the use of the scan tool, refer to the appropriate Diagnostic information.
Refer to SYSTEM WIRING DIAGRAMS .
| WARNING | Disable the airbag system before attempting any steering wheel, steering column, seat belt tensioner, side airbag, 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. |
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| NO AUDIO | 1. Fuse faulty. | 1. Check radio fuse and Ignition-Off Draw (IOD) fuse in Totally Integrated Power Module (TIPM). Replace fuses, if required. |
| 2. Radio connector faulty. | 2. Check for loose or corroded radio connector. Repair, if required. | |
| 3. Wiring faulty. | 3. Check for shorted or open wires. Repair wiring, if required. | |
| 4. Radio ground faulty. | 4. Check for continuity between radio chassis and a known good ground. There should be continuity. Repair ground, if required. | |
| 5. Speakers faulty. | 5. Replace speaker as necessary. | |
| 6. Radio faulty. | 6. Refer to appropriate Diagnostic Service Information. | |
| NO RADIO DISPLAY | 1. Fuse faulty. | 1. Check radio fuse and Ignition-Off Draw (IOD) fuse in Junction Block (JB). Replace fuses, if required. |
| 2. Radio connector faulty. | 2. Check for loose or corroded radio connector. Repair, if required. | |
| 3. Wiring faulty. | 3. Check for battery voltage at radio connector. Repair wiring, if required. | |
| 4. Radio ground faulty. | 4. Check for continuity between radio chassis and a known-good ground. There should be continuity. Repair ground, if required. | |
| 5. Radio faulty. | 5. Refer to appropriate Diagnostic Service Information. | |
| POOR RADIO RECEPTION | 1. Antenna faulty. | 1. See DIAGNOSIS AND TESTING . |
| 2. Radio ground faulty. | 2. Check for continuity between radio chassis and a known-good ground. There should be continuity. Repair ground, if required. | |
| 3. Radio noise suppression faulty. | 3. Repair or replace ground strap as necessary. | |
| 4. Radio faulty. | 4. Refer to appropriate Diagnostic Service Information. | |
| SOUND DISTORTION (VIBRATION FROM SPEAKER AREA, BUZZING - HUMMING) | 1. Door trim panel loose or missing fasteners. | 1. Inspect door trim panel and correct as necessary. Replace any missing fasteners. |
| 2. Water shield loose or misaligned. | 2. Inspect water shield and adjust as required. | |
| 3. Items placed in door trim panel map pockets vibrating or moving from side to side. | 3. Remove items from door trim panel. Ensure that vibration is no longer present. | |
| NO COMPACT DISC/DVD OPERATION | 1. Faulty CD/DVD. | 1. Insert known good CD/DVD and test operation. |
| 2. Foreign material on CD/DVD. | 2. Clean CD/DVD and test operation. | |
| 3. Condensation on CD/DVD or optics. | 3. Allow temperature of vehicle interior to stabilize and test operation. | |
| 4. Faulty CD/DVD player. | 4. Refer to appropriate Diagnostic Service Information. |
AUDIO SYSTEM DIAGNOSIS TABLE
The antenna body and cable connects the antenna mast to the radio. The radio antenna is an electromagnetic circuit component used to capture radio frequency signals that are broadcast by local commercial radio stations in both the Amplitude Modulating (AM) and Frequency Modulating (FM) frequency ranges. These electromagnetic radio frequency signals induce small electrical modulations into the antenna as they move past the mast. The antenna body transfers the weak electromagnetic radio waves induced into the antenna into the center conductor of the flexible primary antenna coaxial cable. The braided outer shield of the antenna coaxial cable is grounded through both the antenna body and the radio chassis, effectively shielding the radio waves as they are conducted to the radio. The radio then tunes and amplifies the weak radio signals into stronger electrical signals in order to operate the audio system speakers.
Scheme 88
The following four tests are used to diagnose the antenna with an ohmmeter
- Test 1 - Mast to ground test
- Test 2 - Tip-of-mast to tip-of-conductor test
- Test 3 - Body ground to battery ground test
- Test 4 - Body ground to antenna coaxial cable shield test.
| WARNING | Disable the airbag system before attempting any steering wheel, steering column, seat belt tensioner, side airbag, 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. |
The ohmmeter test lead connections for each test are shown in the illustration.
Note. This model has a two-piece antenna coaxial cable. Tests 2 and 4 must be conducted in two steps to isolate an antenna cable problem. First, test the primary antenna cable (integral to the antenna body and cable) from the coaxial cable connector behind the right side kick panel to the antenna body. Then, test the secondary antenna cable (instrument panel antenna cable) from the coaxial cable connector behind the right side kick panel to the coaxial cable connector at the radio.
DESCRIPTION
Note. The USB protective door can be serviced separately and does not require the replacement of the entire radio assembly.
The radio receiver operates only when the ignition switch is in the ON or ACCESSORY positions.
For complete circuit diagrams, refer to SYSTEM WIRING DIAGRAMS .
Radio Frequency Interference (RFI) and ElectroMagnetic Interference (EMI) can be produced by any on-board or external source of electromagnetic energy. These electromagnetic energy sources can radiate electromagnetic signals through the air, or conduct them through the vehicle electrical system.
When the audio system converts RFI or EMI to an audible acoustic wave form, it is referred to as radio noise. This undesirable radio noise is generally manifested in the form of "buzzing," "hissing," "popping," "clicking," "crackling," and/or "whirring" sounds. In most cases, RFI and EMI radio noise can be suppressed using a combination of vehicle and component grounding, filtering and shielding techniques. This vehicle is equipped with factory-installed radio noise suppression devices that were designed to minimize exposure to typical sources of RFI and EMI; thereby, minimizing radio noise complaints.
Radio noise suppression is accomplished primarily through circuitry or devices that are integral to the factory-installed radios, audio power amplifiers and other on-board electrical components such as generators, wiper motors, blower motors, and fuel pumps that have been found to be potential sources of RFI or EMI. External radio noise suppression devices that are used on this vehicle to control RFI or EMI, and can be serviced, include the following
- Engine-to-body ground strap - This length of braided ground strap has an eyelet terminal connector crimped to each end. One end is secured to the engine cylinder head(s). The other is secured to the plenum.
- Resistor-type spark plugs - This type of spark plug has an internal resistor connected in series between the spark plug terminal and the center electrode to help reduce the production of electromagnetic radiation that can result in radio noise.
There are two common strategies that can be used to suppress Radio Frequency Interference (RFI) and ElectroMagnetic Interference (EMI) radio noise. The first suppression strategy involves preventing the production of RFI and EMI electromagnetic signals at their sources. The second suppression strategy involves preventing the reception of RFI and EMI electromagnetic signals by the audio system components.
The use of braided ground straps in key locations is part of the RFI and EMI prevention strategy. These ground straps ensure adequate ground paths, particularly for high current components such as many of those found in the starting, charging, ignition, engine control and transmission control systems. An insufficient ground path for any of these high current components may result in radio noise caused by induced voltages created as the high current seeks alternative ground paths through components or circuits intended for use by, or in close proximity to the audio system components or circuits.
Preventing the reception of RFI and EMI is accomplished by ensuring that the audio system components are correctly installed in the vehicle. Loose, corroded or improperly soldered wire harness connections, improperly routed wiring and inadequate audio system component grounding can all contribute to the reception of RFI and EMI. A properly grounded antenna body and radio chassis, as well as a shielded antenna coaxial cable with clean and tight connections will each help reduce the potential for reception of RFI and EMI.
Radio controls are mounted on the back of the steering wheel. The controls provide convenient no-look operation and operate the following functions
- Right side A rocker switch that increases or decreases the volume A push button that selects modes. Repeatedly pressing the button selects from among AM radio, FM radio and CD changer. If the vehicle is equipped with Satellite Digital Audio Radio (SDAR) or the Video Entertainment System™, these are also included in the selection.
- Left side A rocker switch with functions that vary depending on the mode: in a radio mode, the frequency increases or decreases; if a CD is playing, the player skips to the next or previous track; if SDAR is playing the tuner skips to the next or previous channel. A push button that steps through preset selections: if the radio is playing, pressing the button selects the next preset frequency; if a CD is playing, the changer selects the next disc; if SDAR is playing the next preset channel is selected.
The six switches in the two remote radio switch units are normally open, resistor multiplexed momentary switches that are hard wired to the Cab Compartment Node (CCN) through the clockspring. The CCN sends a five volt reference signal to both switch units on one circuit, and senses the status of all of the switches by reading the voltage drop on a second circuit.
When the CCN senses an input (voltage drop) from any one of the remote radio switches, it sends the proper switch status messages on the Controlled Area Network (CAN) to the radio receiver. The electronic circuitry within the radio receiver is programmed to respond to these remote radio switch status messages by adjusting the radio settings as requested. For diagnosis of the CCN or the CAN data bus, the use of a scan tool and the proper Diagnostic article are recommended.
Two wires connected to each speaker, one feed circuit (+) and one return circuit (-), allow the audio output signal electrical current to flow through the voice coil. For complete circuit diagrams, refer to SYSTEM WIRING DIAGRAMS . The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.