Radio/Stereo: Description and Operation
INTRODUCTIONAn audio system is standard factory-installed equipment on this model, unless the vehicle is ordered with an available radio delete option.
Audio System
Several combinations of radio receivers and speaker systems are offered on this model. The standard equipment audio system includes an AM/FM/ cassette (RAS sales code) receiver, and speakers in four locations.
Following are general descriptions of the major components in the standard and optional factory-installed audio systems. Refer to the owner's manual in the vehicle glove box for more information on the features, use and operation of each of the available audio systems.
SYSTEM OPERATION
Radio
Available factory-installed radio receivers for this model include an AM/FM/cassette (RAS sales code), an AM/FM/cassette/5-band graphic equalizer with CD changer control feature (RBN sales code), an AM/FM/ CDI3-band graphic equalizer (RBR sales code), or an AM/FM/CD/cassette/3-band graphic equalizer (RAZ sales code). All factory-installed receivers are stereo Electronically Tuned Radios (ETR) and include an electronic digital clock function.
The radio can only be serviced by an authorized radio repair station. Refer to the latest Warranty Policies and Procedures for a current listing of authorized radio repair stations.
For more information on radio features, setting procedures, and control functions refer to the owner's manual in the vehicle glove box.
Ignition-Off Draw Fuse
All vehicles are equipped with an Ignition-Off Draw (IOD.) fuse that is removed when the vehicle is shipped from the factory This fuse feeds various accessories that require battery current when the ignition switch is in the Off position, including the clock. The fuse is removed to prevent battery discharge during vehicle storage.
When removing or installing the IOD. fuse, it is important that the ignition switch be in the Off position. Failure to place the ignition switch in the Off position can cause the radio display to become scrambled when the IOD. fuse is removed and replaced. Removing and replacing the IOD. fuse again, with the ignition switch in the Off position, will correct the scrambled display condition.
The IOD. fuse should be checked if the radio or clock displays are inoperative. The IOD. fuse is located in the junction block. Refer to the label on the back of the junction block fuse access panel for IOD. fuse identification and location.
Speaker
The standard equipment speaker system includes speakers in four locations. One full-range 15.2 by 22.9 centimeter (6.0 by 9.0 inch) speaker is located in each front door. There is also one full-range 13.3 centimeter (5.25 inch) diameter speaker located in each rear cab side panel for the standard cab and the club cab models, or in each rear door of the quad cab models.
The optional premium speaker system features Infinity model speakers in six locations. Each of the standard front door speakers are replaced with Infinity model speakers that include an integral 30 watt dual amplifier, which is used to drive both the front door speaker and an Infinity tweeter mounted in the A-pillar garnish moulding. Each of the standard rear speakers is replaced by an Infinity model speaker, which is driven by the amplifier in the radio. The total available power of the premium speaker system is about 150 watts.
Filter, Choke, And Speaker Relay
Models equipped with the Infinity premium speaker package use this filter, choke, and speaker relay unit to control battery feed to the two speaker- mounted amplifiers. The filter, choke, and speaker relay unit should be checked if there is no sound output noted from both of the front door speakers and the A-pillar tweeters.
The filter, choke, and speaker relay unit is mounted to the lower instrument panel center brace, inboard of the Central Timer Module (CTM) and directly above the 16-way data link connector. The filter, choke, and speaker relay unit can be accessed for service without instrument panel disassembly or removal.
The filter, choke, and speaker relay unit cannot be repaired and, if faulty or damaged, the unit must be replaced.
Antenna
All models use a fixed-length stainless steel rod-type antenna mast, installed at the right front fender of the vehicle. A plastic sleeve is installed over the length of the mast to reduce wind noise.
The antenna mast is connected to the center wire of the coaxial antenna cable, and is not grounded to any part of the vehicle. To eliminate static, the antenna base must have a good ground. The coaxial antenna cable shield (the outer wire mesh of the cable) is grounded to the antenna base and the radio chassis.
The antenna coaxial cable has an additional disconnect, located near the passenger side end of the instrument panel at the cowl side inner panel. This additional disconnect allows the instrument panel assembly to be removed and installed without removing the radio.
The factory-installed Electronically Tuned Radios (ETRs) automatically compensate for radio antenna trim. Therefore, no antenna trimmer adjustment is required or possible when replacing the receiver or the antenna.
Radio Noise Suppression
Radio Frequency Interference (RFI) and Electro Magnetic Interference (EMI) noise suppression is accomplished primarily through circuitry internal to the radio receivers. These internal suppression devices are only serviced as part of the radio receiver.
External suppression devices that are serviced, and should be checked in the case of RFI or EMI noise complaints, include the following:
- Radio antenna base ground
- Radio chassis ground wire, strap, or bracket
- Engine-to-body ground strap (if the vehicle is so equipped)
- Cab-to-bed ground strap (if the vehicle is so equipped)
- Heater core ground strap (if the vehicle is so equipped)
- Resistor-type spark plugs
- Radio suppression-type secondary ignition wiring.
In addition, if the source of RFI or EMI noise is identified as a component on the vehicle (i.e., generator, blower motor, etc.), the ground path for that component should be checked. If excessive resistance is found in that circuit, repair that circuit as required before considering any component replacement.
If the source of the noise is identified as two-way mobile radio or telephone equipment, check the equipment installation for the following:
. Power connections should be made directly to the battery, and fused as closely to the battery as possible.
- The antenna should be mounted on the roof or toward the rear of the vehicle. Remember that magnetic antenna mounts on the roof panel can adversely affect the operation of an overhead console compass, if the vehicle is so equipped.
- The antenna cable should be fully shielded coaxial cable, should be as short as is practical, and should be routed away from the factory-installed vehicle wire harnesses whenever possible.
- The antenna and cable must be carefully matched to ensure a low Standing Wave Ratio (SWR).
Fleet vehicles are available with an extra-cost RFI suppressed Powertrain Control Module (PCM). This unit reduces interference generated by the PCM on some radio frequencies used in two-way radio communications. However, this unit will not resolve complaints of RFI in the commercial AM or FM radio frequency ranges.