Section 13-02: Speedometer/Odometer
1993 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Speedometer/Odometer

The Ford Master Parts catalog shows the proper speedometer transmission gears to use for various rear axle and tire size combinations. The correct gears must be used to comply with Federal law.

The diagnosis charts should be used to isolate concerns in the non-electronic speedometer.  

PINPOINT TEST A: SPEEDOMETER/ODOMETER NOISY, ERRATIC, INOPERATIVE OR INACCURATE

 

A1 VERIFY CONDITION

Noisy
GO to A2.

Erratic or pointer waver
GO to A3.

Inoperative speed indication
GO to A7.

Inoperative odometer
GO to A8.

Inaccurate speed indication
GO to A15.

 

A2 CHECK FOR NOISE

  • With engine running in NEUTRAL, check for noise.
  • Is noise present?
Yes
CHECK for other causes of vehicle noise.

No
GO to A3.

 

A3 CHECK CABLE

  • Check cable for kinks or bends.
  • Is cable OK?
Yes
GO to A4.

No
If kinks are severe, REPLACE cable. For minor bends, ADJUST cable routing to obtain generous curves and RECHECK for condition resolution.

 

A4 CHECK CABLE

  • Disconnect cable and check core for kinks, burrs or bent tips.
  • Is cable OK?
Yes
GO to A5.

No
REPLACE cable.

 

A5 CHECK VEHICLE SPEED SENSOR (VSS) 9E731

  • Remove vehicle speed sensor (VSS), check for erratic or noisy operation.
  • Is speed sensor OK?
Yes
GO to A6.

No
REPLACE vehicle speed sensor (VSS).

 

A6 CHECK DRIVEN GEAR

  • Check for damaged driven gear.
  • Is driven gear OK?
Yes
REPLACE speedometer head.

No
REPLACE gear.

 

A7 CHECK ODOMETER

  • Check to see that odometer is operating.
  • Does odometer operate properly?
Yes
REPLACE speedometer head.

No
GO to A9.

 

A8 CHECK POINTER OPERATION

  • Check to see that pointer operates.
  • Does pointer operate properly?
No
GO to A9.

Yes
REPLACE speedometer head.

 

A9 VERIFY CABLE CONNECTIONS

  • Check and verify that cable is properly connected to speedometer and to speed sensor.
  • Is cable connected properly?
Yes
GO to A10.

No
SERVICE cable connections as required.

 

A10 CHECK MAGNET SHAFT

  • Disconnect cable and check that magnet shaft in speedometer head turns freely.
  • Does magnet shaft turn freely?
Yes
GO to A11.

No
REPLACE speedometer head.

 

A11 CHECK DRIVE AND DRIVEN GEAR

  • Check drive and driven gear for damage or wear.
  • Are both gears OK?
Yes
GO to A12.

No
REPLACE damaged gear.

 

A12 CHECK CABLE

  • Check speedometer cable for kinks or improper routing.
  • Is cable OK?
Yes
GO to A13.

No
REPLACE cable.

 

A13 CHECK SENSOR SHAFT

  • Disconnect cable from vehicle speed sensor (VSS). Remove sensor and check that shaft in sensor turns freely.
  • Does sensor shaft turn freely?
Yes
GO to A14.

No
REPLACE vehicle speed sensor (VSS).

 

A14 CHECK CORE

  • Check for broken core.
  • Is core OK?
Yes
If core is seized and will not turn, REPLACE cable.

No
REPLACE cable.

 

A15 CHECK ODOMETER/SPEEDOMETER ACCURACY

  • Check accuracy of odometer over a measured distance. Refer to Speedometer Calibration Tolerance Specifications.
  • Is odometer accurate?
Yes
REPLACE speedometer head.

No
GO to A16.

 

A16 CHECK DRIVEN GEAR

  • Check for proper driven gear.
  • Is driven gear correct?
Yes
GO to A17.

No
REPLACE gear.

 

A17 CHECK DRIVE GEAR, AXLE AND TIRES

  • Check for proper drive gear, axle and tires.
  • Are drive gear, axle and tires correct?
Yes
REPLACE speedometer assembly.

No
REPLACE incorrect component or driven gear.