Speedometer not working properly?

Tiny
MASTERRYK
  • MEMBER
  • 1999 GMC SAVANA
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 225,000 MILES
Speedometer reads 60 to 70 MPH when traveling 30 MPH. Anti-lock came on.
Monday, February 13th, 2023 AT 1:12 PM

2 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

There is a vehicle speed sensor at the rear of the transmission. See pic below. By chance have you checked it? Also, if you have a live data scan tool, you can check if the sensor is sending the wrong signal while driving.

Let me know.

Take care,

Joe
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Tuesday, February 14th, 2023 AT 11:27 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,638 POSTS
Hello,

This can be caused by one of two things, the VSS (vehicle speed sensor), the ABS module which is what I am leaning towards because of the ABS light. We should run the codes, here is a guide to show you how:

https://www.2carpros.com/articles/anti-lock-system-testing-and-repair-abs

The first thing we should replace is the VSS (vehicle speed sensor) because it is cheap. Here is the location so you can check the electrical connector and sensor and I have included how to change out the ABS module in case you need it. Please check the images below
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Tuesday, February 14th, 2023 AT 11:44 AM

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