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Dan, Buick Technician
Category: Buick
Satisfied Customers: 3490
Experience:  GM trained, GM Mark of Excellence, ASE Master Certified
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1997 buick lesabre custom: jump..steady speed..real fast..speedometer

Customer Question

1997 buick lesabre custom the speedometer will jump around sometime when I am not moving it will go to 40 or sometimes all the way over. sometimes when going a steady speed the speerdometer will go to 0 or real fast. Cruisecontrol always works even when speedometer is acting up. I have put 3 different speedsensors. Every thing works great but the speedometer
Submitted: 6 years ago.
Category: Buick
Expert:  Dan replied 6 years ago.

Here is a basic diagnostic chart from GM pertaining to the speedo being inop. If the cruise control and transmission are working ok I would suspect a bad instrument cluster.


Speedometer and/or Odometer Inoperative







Did you perform the Instrument Cluster System Check?


Go to Step 2

Go to Instrument Cluster System Check


  1. Disconnect the PCM connector C1.
  2. Connect a signal generator I/P test J 33431-C to PCM connector C1, terminal 55.
  3. Connect J 33431-C ground terminal to a good chassis ground.
  4. Set the signal generator I/P tester J 33431-C to 54 mph.
  5. Turn the ignition switch to RUN.

Does the speedometer read the specified value?

54 mph

Go to Step 4

Go to Step 3


Inspect CKT 817 (DK GRN/WHT) for the following conditions:

  1. A short to ground
  2. A short to voltage
  3. An open

Is CKT 817 OK?


Go to Step 6

Go to Step 5


  1. Inspect for a poor connection at the PCM connector C1, terminal 55.
  2. If the terminal contact is OK, refer to Engine Controls.

Did you find and correct the condition?


Go to Instrument Cluster System Check



Repair CKT 817 (DK GRN/WHT). Refer to Repairing Damaged Wire Insulation in Wiring Systems.

Did you complete the repair?


Go to Instrument Cluster System Check


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