Audio System: Notes

Some of the radios are on the PCI Bus system. The PCI Bus inputs into the radio are used for VF dimming, remote steering wheel controls and cabin EQ preference. PCI Bus outputs from the radio are used for the Name Brand Speaker (NBS) relay activation, as well as cabin EQ preference.

The radios have the capability of containing multiple vehicle unique equalization curves (cabin EQ preferences) within the radio. These curves will reside in the radio's flash memory. The radio is capable of storing up to 20 unique equalization curves. The latent curves can be selected via the Front Control Module transmitting a PCI Bus message to the radio in response to a radio request for equalization message. Upon receipt of a valid equalization select message response, the radio will switch to output the corresponding equalization curve.

All the radios are capable of displaying faults and allowing certain actuation tests through the use of the DRBIII®. When attempting to perform PCI Bus diagnostics, the first step is to identify the radio in use in the vehicle.

When trouble shooting output shorts or "output" error messages, the following applies:

On radios without an external amplifier, the term output 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 output DTC with this type of system, the speaker, radio, or wiring could be at fault.

On radios with an external amplifier, the term "output" 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 output DTC on this type of system would only refer to this circuit. A faulty speaker could not cause this DTC.