Speedometer/odometer stopped working today (panel not displaying any data). where do i start?

There is no fuse for just the odometer, has main fuses for the whole instrument cluster . Odometer not working? instrument cluster problem. Have it checked by a professional repair shop.

Odometers
Each instrument panel cluster (IPC) is equipped with a season odometer and 2 trip odometers. The IPC uses the odometer rolling count message from the powertrain control module (PCM). The rolling count value is determined by counting the speed pulses from the vehicle speed signal (VSS). The IPC uses the rolling count data from the PCM and a software program to determine vehicle mileage. The odometers can be displayed in miles or kilometers. The units displayed is switched between English and metric by pressing the menu button on the driver information center (DIC) until the units mode is displayed. Pressing the set/reset button will select between English or Metric. . When the set/reset button is pressed to show the odometer in metric, km and the number will be displayed. When the odometer is in English, MI and the number will be displayed.


Season Odometer
The season odometer displays the total accumulated miles or kilometers of the vehicle. This value is permanently stored in the IPC. If an odometer malfunction occurs or if the IPC must be replaced, an authorized Delco service center must be contacted to program proper vehicle specifics, including mileage, for the IPC. The season odometer is capable of displaying 999,999 kilometers or 999,999 miles depending on units selected. Leading zeros are not displayed. The display will not roll-over to 000,000 if the maximum displayed miles or kilometers are reached. If the display limit is exceeded, the maximum value (999,999) is displayed. If the mileage is above 621,503 miles and metric units are selected the odometer shall display 999,999 km.


Circuit/System Testing
Ignition OFF, raise the vehicles drive wheels.
Engine ON, transmission in drive, verify the scan tool Vehicle Speed Sensor parameter matches the speedometer display.
? If the Vehicle Speed Sensor parameter does not match the speedometer display, replace the IPC.
Verify that the odometer is operating properly.
? If the odometer is not operating properly, replace the IPC.

you tell us everything except the most important facts

year make model

This all points to a BCM or communication issue. You need an auto electrician with a pro grade scan tool computer. They can record the live data as it all happens and why?

Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the body control module (BCM). The engine control module (ECM) calculates the vehicle speed based on the controller area network (CAN) serial data message indicating the wheel reference speed from the electronic brake control module (EBCM). The ECM sends a CAN serial data message to the BCM indicating the vehicle speed. The BCM sends a class 2 message to the IPC indicating the vehicle speed.
The speedometer defaults to 0 km/h (0 mph) when any of the following occur:
• The EBCM detects a malfunction in the vehicle speed sensor circuit.
• The ECM detects a loss of CAN communications with the EBCM.
• The BCM detects a loss of CAN communications with the ECM.
• The IPC detects a loss of class 2 communications with the BCM.

Having the vehicle scanned for codes would probably point you in a correct diagnostic direction .

Odometer
The odometer is an electronic digital display. Digits displayed are illuminated by the odometer backlight bulb. The odometer backlight bulb brightness is controlled by class 2 messages from the BCM to adjust the display for daylight and instrument panel dimming operation. The trip odometer and total odometer will show in this display area. The push button in the lower right side of the speedometer is used to toggle between the trip and total odometer readings. To reset the trip odometer, push and hold the button down for at least two seconds. The total odometer display has six digits with no decimal display. The trip odometer has four digits including a decimal point and indicates tenths of a mile or kilometer.
The body control module (BCM) stores the vehicle mileage. If the BCM fails, the cluster will display the last valid mileage that was sent before the BCM failed. For replacement of the BCM refer to the BCM section of this service manual. Replacement instrument clusters do not require odometer pre-setting before installation. If the instrument cluster is replaced, the mileage stored in the BCM will be sent to the new cluster via serial data, and shown in the odometer display.

Your best bet , take it to a qualified repair shop.

It wouldn't be a ground problem If it were the whole instrument cluster would be dead . Checking the BCM an the IPC for DTC'S - diagnostic trouble codes is the proper way to diagnose this type problem . Not worrying about grounds .
Odometer
The vehicle odometer is calculated and stored electronically in the body control module (BCM) and is sent via the serial data circuit to the instrument panel cluster (IPC) for display. The BCM calculates and stores the mileage based on the vehicle speed serial data information from the PCM/ECM. The IPC displays the season odometer information from the BCM in the driver information center (DIC). The odometer will display error if the IPC detects an invalid odometer data from the BCM. After an invalid odometer data is received from the BCM, the IPC will display the last known odometer reading for 1.5 seconds before error is displayed in the DIC.
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on serial data message from the body control module (BCM). The BCM receives vehicle speed data from the PCM/ECM via the serial data circuit. The speedometer will default to 0 km/h (0 mph) if:
• The PCM/ECM detects a malfunction in the vehicle speed sensor circuit.
• The BCM detects a loss of serial data communications with the PCM/ECM.
• The IPC detects a loss of serial data communications with the BCM.

Your best bet would be to take it to the dealer !

Before doing something drastic ,have it checked out for DTC'S - diagnostic trouble codes . It may not be the anti-theft system ,gauges going flat would be more like a communication problem between modules . PCM / BCM / instrument cluster etc.. That also could cause theft light coming on . If your not sure what to look for ,take it to a ASE certified professional . You may render your vehicle useless if you don't know what your doing .
Serial Data Power Mode Master
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 body control module (BCM). The PMM receives 3 discrete ignition switch signals to differentiate which power mode will be sent over the Serial Data circuits. The 3-wire Ignition Switch table below illustrates the state of these inputs in correspondence to the ignition switch position:
Serial Data Messages The modules that depend exclusively on serial data messages for power modes. stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to RUN. In this state, the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to OFF-AWAKE. In this state, the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.
Indicators and Warning Messages
Refer to Indicator/Warning Message Description and Operation .
Engine Coolant Temperature Gage
The instrument panel cluster (IPC) displays the engine coolant temperature as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the PCM/ECM indicating the engine coolant temperature. The engine coolant temperature gage defaults to 38?°C (100?°F) if:
?€¢
The PCM/ECM detects a malfunction in the engine coolant temperature sensor circuit.

?€¢
The IPC detects a loss of serial data communications from the BCM.

Fuel Gage
The instrument panel cluster (IPC) displays the fuel level as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the fuel level. The fuel gage defaults to E (empty) if:
?€¢
The PCM/ECM detects a malfunction in the fuel level sensor circuit.

?€¢
The IPC detects a loss of serial data communications from the BCM.

When the fuel level is less than 14 percent, the low fuel indicator illuminates.
Odometer
The instrument panel cluster (IPC) contains a season odometer and a trip odometer. Momentarily press the trip/reset switch in order to toggle between the season odometer and the trip odometer. Press the trip/reset switch for greater than 2 seconds, while the trip odometer is displayed, in order to reset the trip odometer. The odometer is calculated and stored electronically in the body control module (BCM). The BCM uses the vehicle speed information from the powertrain control module (PCM) to calculate the odometer. The odometer displays 'error' if an internal IPC memory failure is detected. The IPC stores a backup copy of the odometer value incase the IPC stops receiving a valid odometer value from the BCM.
Speedometer
The instrument panel cluster (IPC) displays the vehicle speed based on the information from the ECM/PCM. The IPC receives the vehicle speed information from the BCM via the serial data circuit. The speedometer defaults to 0 kmh (0 mph) when the following occurs:
?€¢
The powertrain control module (PCM) or the engine control module (ECM) detects a malfunction in the vehicle speed sensor circuit.

?€¢
The IPC detects a loss of serial data communication from the BCM.

Tachometer
The instrument panel cluster (IPC) displays the engine speed as determined by the powertrain control module (PCM) or the engine control module (ECM). The IPC receives a serial data message from the body control module (BCM) indicating the engine speed. The tachometer will default to 0 RPM if:
?€¢
The PCM/ECM detects a malfunction in the engine speed sensor circuit.

?€¢
The IPC detects a loss of serial data communication from the BCM.

If the speedometer stops working the odometer stops also. Sounds like it is stuck in first gear. The RPM went up because the throttle was response to pedal but transmission not response. Check transmission fluid color. Whip off dipstick on a white paper towel look for gray if see any that is metal shavings and transmission is bad.

if the odometer is working then the problem is with the speedometer head unit as the odometer gets its information from the same source as the speedometer. you can have the speedometer head checked and fixed if its fixable.

there is a regulator for the display brightness, you may have it turn'd down or it has stopped working;. it controls the brightness at which the dash lights are. usually has a speedo sign on it. goes up and down. it works with the main light and is conecter to them on the same lighting board if it has gone then a new light swtch control switch will be needed.

Section 13-01: Instrument Cluster—Conventional 1995 Thunderbird, Cougar Workshop Manual REMOVAL AND INSTALLATION Instrument Cluster Removal and Installation

1. Disconnect battery ground cable (14301) .

1. Remove screws holding instrument panel reinforcement (017A28) .

1. Remove screws holding instrument panel lower shield (045G02) .

1. Remove fasteners holding steering wheel column as outlined in Section 11-04 . Gently lower steering column.

1. Remove fasteners holding the instrument panel finish panel (044D70) and gently pry off.
   
   
   
   

1. Remove four instrument cluster retaining screws. (Do not remove screws from the instrument cluster main lens (10887) and instrument cluster mask (10890) ).

1. Slide the instrument cluster (10849) to the right of the instrument panel opening and unhook the instrument panel harness from the back of the instrument cluster .

1. Remove the instrument cluster from the instrument panel (04320) .

-----------------------
Speedometer/Odometer Federal law requires that the odometer in any replacement speedometer (17255) must register the same mileage as that registered in the removed speedometer . Since the speedometer mileage cannot be reset on this unit, affix odometer sticker to driver's door pillar and record original vehicle mileage. Removal

1. Disconnect battery ground cable (14301) .

1. Remove the instrument cluster (10849) as outlined.

1. Remove seven screws retaining the instrument cluster mask (10890) and instrument cluster main lens (10887) .

1. Remove speedometer assembly.

Installation

1. Position the speedometer assembly to the instrument cluster back plate (10848) and install.

1. Position the instrument cluster mask and instrument cluster main lens to the instrument cluster back plate and install the seven retaining screws.

1. Install the instrument cluster as outlined.

1. Connect battery ground cable and check the operation of the speedometer .

please rate if this helps