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Dan
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

Step

Action

Value(s)

Yes

No

1

Did you perform the Instrument Cluster System Check?

--

Go to Step 2

Go to Instrument Cluster System Check

2

  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

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

4

  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

--

5

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