I have a 2002 Deville DTS which at first lost the turn signals, tachometer and speedometer. Now every other electrical component(ie feul, lights, power Windows, doors, as well as locks) all fail to wo

Do you know how to do automotive electrical testing ? Checking power and grounds . Hooking up a scan tool that can communicate with all the modules on the vehicle . The insturment cluster is a module too ,has a microprocessor inside . All the modules on the vehicle are connected through a serial data network . Class 2 . All it takes is one messed up module to short out the network an the vehicle will have all kind of electrical problems , like you won't believe . I see this all the time and the odds of you fixing this is probably not good . You have no idea of the complexity of these systems . So before you make the problem worst have the cadillac dealer check it out .
Body Control System Description and Operation
Table 1: 4-Wire Ignition Switch Table
The body control system consists of the following 3 modules:
• The Dash Integration Module (DIM)
• The Instrument Panel Module (IPM)
• The Rear Integration Module (RIM)
Each of the 3 body control modules integrate a number of functional systems under the control of a single module. Each module is connected to the Class 2 serial data circuit, many of the control functions are implemented by Class 2 messages.

Dash Integration Module (DIM)
The various DIM input and output circuits are described in the corresponding functional areas as indicated on the DIM electrical schematics.
The DIM functions include the following:
• Class 2 communication requiring DIM interaction.
• Control of exterior lamps.
• Control of front fog lights.
• Control of the headlights.
• Headlamps on with wiper input.
• Hood ajar switch input w/export.
• Horn relay control.
• Interior lamps incandescent dimming.
• Low side temperature for HVAC compressor.
• Power moding control over Class 2 serial data circuit.
• Reverse lockout solenoid control.
• Steering wheel controls input.
• Storage of the clock settings and, sending a message out on the class 2 serial data circuit in response to requests from other modules.
Serial Data Power Mode
On vehicles that have several control modules connected by serial data circuits, one module is the power mode master (PMM). On this vehicle the PMM is the DIM. The PMM receives 4 signals from the ignition switch.
To determine the correct power mode the PMM uses the following circuits:
• Accessory voltage
• Ignition 1 voltage
• Ignition 3 voltage
• Off/Run/Crank voltage