Audio System

AUDIO SYSTEMS
There are 3 radio systems available in the 1999 Grand Cherokee.

The sales codes for the radios are:
RAS-AM/FM cassette two band E.Q. no external amplifier no PCI bus diagnostics.
RBN-AM/FM cassette 3 band E.Q. external amplifier with external CD changer PCI diagnostics. RAZ-AM/FM cassette and CD player 3 band E.Q. PCI diagnostics available with or without an external amplifier.

The RBN and RAZ are capable of displaying faults and allowing certain actuation tests through the use of the DRB III. When attempting to perform PCI diagnostics the first step is to identify the radio in use in the vehicle. Use the above list to help determine the audio system being serviced.

NOTE: ATTEMPTS TO COMMUNICATE WITH THE RAS RADIO THROUGH THE DRB III WILL RESULT IN A COMMUNICATION ERROR BECAUSE THE RADIO IS NOT ON THE BUS THIS MAY LEAD TO LOST TIME A NO PROBLEM FOUND RESULT.

Troubleshooting Hints For Audio Systems
When troubleshooting channel shorts or "channel" error messages the following applies:

On radios with out an external amplifier the term channel refers to the path between the radio and the speaker. This type of circuit can be monitored all the way through the speaker connections by the radio assembly. When the radio displays a shorted channel DTC with this type of system the speaker radio or wiring could be at fault. The channel DTC could refer to a front or rear channel or a left or right channel. The reason for the difference is the pairing of the output sections of the radio. Some are paired left and right others are paired front and rear.

On radios with an external amplifier the term "channel" refers to the circuit between the radio connector and the amplifier. The radio is capable of monitoring only this portion and can tell nothing about the circuit between the amplifier and the speakers. Consequently a shorted channel DTC on this type of system would only refer to this circuit. A faulty speaker could not cause this DTC.

These radios can be controlled via remote radio Switches (optional). These Switches are located on the back side of the steering wheel. They control volume preset bank selection seek and scan functions. There are no DTCs associated with the remote control Switches.

These functions are inputs to the body controller and can be read with the DRB III under "body" systems sensor displays. The Switches are a multiplexed signal to the BCM. The remote radio control circuit is a five volt line that is pulled to ground through different value resistors built into the switches. This causes a voltage drop to be seen by the body controller and it sends a specific message to the radio on the PCI bus line. The radio then responds to the message.

This circuit is fairly simple to troubleshoot. The circuit must be complete from the Switches in the steering wheel to the BCM. The ground must be complete so that the Switches can cause the voltage drop for the BCM to see. The circuit passes through the clock spring so continuity through this device must be verified.

CD Changer Diagnostic Trouble Codes
The CD changer has diagnostic trouble codes (DTCs) that are separate from the radio or "in dash" CD player. These codes are found using the DRB III and accessing DTCs under audio systems. There are four codes that are reported by the external CD changer. IMPROPER DISC CD PLAY FAILURE CD TEMPERATURE HIGH and CD MECHANISM FAILURE. They are all due to improper use or internal failure of the CD changer. If any of these codes exist check the changer for obvious problems such as wrong type of CD upside down CD scratched or dirty CD foreign objects inserted into changer etc. Correct the problem. Clear DTCs. Then check to see if the DTC(s) return. If they do replace the changer.