# Speedometer

**URL:** <https://community.cartalk.com/t/speedometer/12917>\
**Category:** Maintenance/Repairs\
**Tags:** speedometer\
**Created:** [April 15, 2008, 9:55pm UTC](https://community.cartalk.com/t/speedometer/12917 "2008-04-15T21:55:30Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![fmoose](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@fmoose](https://community.cartalk.com/u/fmoose)\
**Post date:** [April 15, 2008, 9:55pm UTC](https://community.cartalk.com/t/speedometer/12917/1 "2008-04-15T21:55:30Z")

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We have a 2003 Chev Traiblazer with 70,000 miles on it. The speedometer is no longer accurate. Sometimes we start off at 35 mpg and sometimes at 75 mph. Is this a major fix in terms of money or a simple cable replacement. Please let me know as we don’t want to spend a great deal of money at the present time.  
  
 Thank You  
  
 Regina

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**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\
**Post date:** [April 15, 2008, 11:30pm UTC](https://community.cartalk.com/t/speedometer/12917/2 "2008-04-15T23:30:03Z")

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This truck does not use a speedo cable. It uses a VSS (vehicle speed sensor) attached to the transmission. The sensor replacement is easy, but the system will need to be diagnosed to determine if the VSS is bad or the electronic speedometer in the dash. This can be done by a competent shop with a proper ODB-II scanner, not a simple code reader, like at Autozone. The ECM in this truck monitors the VSS to determine things like shift points for the transmission, and can be seen on a scanner. This will help narrow down the problem.

If the CEL (check engine light) is not on, I’m leaning towards a speedometer problem, not the VSS.

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**Author:** ![hellokit](https://avatars.discourse-cdn.com/v4/letter/h/6a8cbe/32.png) [@hellokit](https://community.cartalk.com/u/hellokit)\
**Post date:** [April 15, 2008, 11:49pm UTC](https://community.cartalk.com/t/speedometer/12917/3 "2008-04-15T23:49:03Z")

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When the truck isn’t moving, there is no (electrical) signal from that sensor to the engine computer. So, I think the problem is from the engine computer (which sends the speed signal to the instrument cluster, to the speedometer) and the speedometer, itself. This problem may not turn on the check engine light.  
Unless you can use a wiring diagram and an electrical multimeter, a repair shop is the way to go.

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**Author:** ![fmoose](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@fmoose](https://community.cartalk.com/u/fmoose)\
**Post date:** [April 17, 2008, 6:40am UTC](https://community.cartalk.com/t/speedometer/12917/4 "2008-04-17T06:40:33Z")

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Thank You - I will post you back when I get the scoop from the Chev Dealer in town. I appreciate your take on it.  
Regina

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**Author:** ![fmoose](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@fmoose](https://community.cartalk.com/u/fmoose)\
**Post date:** [April 17, 2008, 6:41am UTC](https://community.cartalk.com/t/speedometer/12917/5 "2008-04-17T06:41:19Z")

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Thank You - I will post you back when I get the scoop from the Chev Dealer in town. I appreciate your take on it.  
Regina

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**Author:** ![fmoose](https://avatars.discourse-cdn.com/v4/letter/f/f07891/32.png) [@fmoose](https://community.cartalk.com/u/fmoose)\
**Post date:** [April 17, 2008, 6:42am UTC](https://community.cartalk.com/t/speedometer/12917/6 "2008-04-17T06:42:26Z")

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Thank You - I will post you back when I get the scoop from the Chev Dealer in town. I appreciate your take on it.  
Regina