Speedometer not working properly

Welcome to 2CarPros.

First, are you using the OEM size tires? A larger tire can cause this. If they are correct, then I can tell you there was a technical service bulletin related to a non-working or inaccurate speedometer issue. It did require the reprogramming of the select modules in the vehicle based on specific options. I will attach the TSB so you can review the problems and fixes.

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1999 Ford Truck Ranger 2WD V6-3.0L VIN U
Speedometer/Odometer - Inaccurate/Inoperative
Vehicle Brakes and Traction Control Relays and Modules - Brakes and Traction Control Technical Service Bulletins By Symptom Speedometer/Odometer - Inaccurate/Inoperative
SPEEDOMETER/ODOMETER - INACCURATE/INOPERATIVE
Article No.
99-26-4

12/27/99

SPEEDOMETER - INACCURATE SPEEDOMETER READINGS

FORD:
1998-2000 EXPLORER, MOUNTAINEER, RANGER

This TSB article is being republished in its entirety to include 2000 model year vehicles.

ISSUE
The vehicle odometer/speedometer may be inoperative or inaccurate as well as Malfunction Indicator Lamp (MIL) illuminated after the Generic Electronic Module (GEM), Central Timer Module (CTM), or the 4-Wheel Anti-lock Brake System (4WABS) Module has been replaced. This may be caused by either the GEM, CTM, or the 4WABS Module tire and axle size calibration.

ACTION
Reprogram the GEM, CTM, or 4WABS Module to match the vehicle attributes. Refer to the following Service Procedure for details.

SERVICE PROCEDURE

In the event a 1998 through 2000 Ranger GEM/CTM/4WABS or a 1998 through 2000 Explorer/Mountaineer 4WABS/C TM component requires service or replacement, the module(s) must be configured for proper operation using a New Generation Star (NGS) Tester and version 6.0 Service function card. If you do not have version 6.0 loaded, use the latest version Service Bay Technical System (SBTS) CD to download NGS Service Function Card Version 6.0 software to the green NGS service card for configuring modules. To configure modules, follow these instructions:

1. SELECT: SERVICE BAY FUNCTIONS

2. SELECT: GEM, CTM or ABS

3. For ABS, proceed to Step 4. For GEM or CTM,

SELECT: CUSTOMER PREFERENCES

4. SELECT: TIRE SIZE/AXLE RATIO
CONFIGURE

a. The NGS Tester will display "DETERMINING MODULE PROTOCOL, PLEASE WAIT"

b. When NGS Tester is ready, press [TRIGGER] to continue.

5. ENTER TIRE SIZE/REVOLUTIONS PER MILE (REV/MILE)

pic 1

NOTE
THE TIRE SIZE MUST BE ENTERED AS A REV/MILE CALCULATION. REFER TO THE REV/MILE CHART FOR THE CORRECT CALCULATION.

6. ENTER AXLE/TONE RING SIZE

NOTE
4X2 RANGERS EQUIPPED WITH A 2.5L OR 3.0L ENGINE HAVE A 7.5" AXLE. 4X4 AND 4.0L RANGERS HAVE AN 8.8" AXLE. ALL EXPLORERS/MOUNTAINEERS HAVE AN 8.8" AXLE. IF THE SPECIFIC AXLE CANNOT BE SELECTED, ENTER THE AXLE TONE RING TOOTH SIZE USING (00102) FOR 7.5" AXLES AND (00108) FOR 8.8" AXLES.

7. ENTER OPTIONS

NOTE
SELECT 4WABS, RABS, OR NA (IF NOT EQUIPPED).

8. ENTER VEHICLE

9. SELECT: DONE - The NGS Tester will display "MODULE CONFIGURATION COMPLETE." The module is now properly configured. Press [TRIGGER] to exit.

10. Verify with road test.

OTHER APPLICABLE ARTICLES: NONE

SUPERSEDES: 99-18-13

WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty Coverage

OPERATION DESCRIPTION TIME 992604A Reprogram Generic 0.7 Hr. Electronic Module (GEM), Central Timer Module (CTM), Or 4-Wheel Anti-Lock Brake System (4WABS) Module

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Let me know if you have questions. Since your vehicle is not 4wd, chances are the only update needed will be to the GEM.

Take care,
Joe