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speedometer pontiac issue
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joemost
New User
Jan 29, 2014, 5:03 AM
Post #1 of 2
(1199 views)
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speedometer pontiac issue
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I have an old mini van... which I use for a work van.. it is a 1994 pontiac transport. Everything works great on it except for the speedometer.
The speedometer goes all crazy when I am driving it. It isnt just blank....but itll say I am going 80 mph when I am going 30. I usually just used my gps to track speed...because it actually works really well. But I can't currently get it to pass inspection because no working speedometer.
I tried replacing the Vechile speed sensor... did not have any difference on the speedometer. Any thoughts or ideas would be amazingly helpful.
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Discretesignals
Ultimate Carjunky
/ Moderator
Jan 29, 2014, 5:18 AM
Post #2 of 2
(1186 views)
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Re: speedometer pontiac issue
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Need to find someone with an enhanced scan tool that can plug into the PCM and see what the VSS information is while the speedo is not registering correctly. That will tell you if you have a cluster problem or some other problem such as a speed buffer issue or electrical interference. You can also watch the signals on a lab scope. The VSS puts out an ac voltage waveform which goes to a speed buffer. The speed buffer converts it to a digital signal that is sent to the PCM, instrument cluster, and the cruise control module. Monitoring those signals can give you idea of what the culprit is.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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