GM Service Manual Online
For 1990-2009 cars only

Radio Chime Circuits

All chimes are activated via the radio according to messages it receives on the class 2 serial data line. The radio sends the required chime signals to the radio amplifier, which sounds the chime through the LF Speaker.

Fasten Belts Chime

If the driver's seat belt is unbuckled, the LH front seat belt switch closes, which applies a ground signal input to the Sensing and Diagnostic Module (SDM). The SDM sends a message on the Class 2 serial data line to the instrument cluster (IPC), indicating that the seat belt switch is closed. When the ignition switch is turned to START or ON, the IPC initiates the fasten seat belts warning. The IPC illuminates the FASTEN BELTS indicator for up to 72 seconds. At the same time, the IPC sends a message on the class 2 serial data line requesting the radio to activate the five-pulse fasten belts chime. If the driver's seat belt is buckled during the 5-pulse chime period, the chime stops and the indicator turns off.

Key-in-Ignition Chime

The Key-In-Ignition Warning chime sounds when the key is in the ignition, not in the ON or START position and the LH front door is open. Inserting a key in the ignition switch closes the ignition key warning switch, which applies a ground input to the Instrument Panel Integration Module (IPM). The IPM sends a message on the class 2 serial data line to the Rear Integration Module (RIM), signalling that the key in ignition switch is closed. Opening the LH front door closes the LH front door jamb switch. The LH Front Door Module (LFDM) senses the switch closure, and sends a message to the RIM on the class 2 serial data line, signalling that the door is open. If the conditions to activate the chime are met, the RIM sends a message on the Class 2 serial data line requesting the radio to activate the Key-in-Ignition Chime.

Lamps On Chime

The Lamps On Chime activates with the headlamp switch in HEAD or PARK position, the LH front door open and the ignition switch in OFF or ACC. When the headlamp switch is in HEAD or PARK, switch contacts close to provide a ground input on the corresponding circuit to the DIM, which in turn, turns on the lamps. Opening the LH front door closes the LH front door jamb switch. The LH Front Door Module (LFDM) senses the switch closure, and sends a message to the DIM on the class 2 serial data line, signalling that the door is open. If the conditions to activate the chime are met, the DIM sends a message on the Class 2 serial data line requesting the radio to activate the Lamps On chime.

Turn Signal On Chime

The Turn Signal On chime activates if a turn signal remains on and the vehicle has travelled more than 1.3 km (0.8 mi). The flasher module provides the LH and RH turn signal inputs to the Instrument Cluster (IPC). The Powertrain Control Module (PCM) supplies the vehicle speed input to the IPC. When the conditions to activate the chime are met, the IPC sends a message on the Class 2 serial data line to the radio to activate the Turn Signal On chime. The chime sounds once per flash of the turn signal as long as the turn signal remains on.