Speedometer not working properly

1999 MERCURY COUGAR
250,000 MILES • 2.0L • 4 CYL • 2WD • MANUAL
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WISH30
  • MEMBER
  • 124 POSTS
I would like to ask one more question, about the speedometer, does someone have an idea what can cause the problem?
The problem is: When you drive, the needle meter show the correct speed, but the digital meter show incorrect numbers. For example you drive 50kmh, and numbers say 40. When you stop, needle goes to 0, and digital numbers stuck to some value as 15 kmh or 20-25 kmh.
Oct 13, 2020 at 7:59 PM
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JACOBANDNICKOLAS
  • CERTIFIED EXPERT
  • 110,175 POSTS
Hi,

In most cases, this type of an issue is caused by excessive resistance in the circuit. Have you checked wiring under the dash to the instrument panel? Also, on the transmission case is the vehicle speed sensor (VSS). Check to make sure the connection is tight, not damaged, and there is no corrosion at the connection. (see pic 1).

Let me know.
Joe
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Oct 14, 2020 at 7:22 PM