speedometer

2000 GMC C3500
150,000 MILES • V8 • 4WD • AUTOMATIC
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PACHYAUTO63
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Is there a p-sensor in the transmission? I replaced all speed sensors and neutral switch ,but when i drive the speedometer goes crazy up and down. what is going on?
Nov 17, 2017 at 8:45 AM
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F4I_GUY
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When you say you replaced all speed sensors, which sensors are you referring to? Did you replace the vehicle speed sensor located on the transmission output side or the wheel speed sensors located at each wheel?
Nov 17, 2017 at 1:34 PM
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PACHYAUTO63
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transmission output side.
Nov 17, 2017 at 1:55 PM
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JIS001
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Is this an automatic? Also is the truck 4 wheel drive? If automatic do you know which transmission you have on here? Is it the 4L60E or the 4L80E?
Nov 19, 2017 at 6:20 PM
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BARBARA1963
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4l80e
Nov 24, 2017 at 1:29 AM
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STRAILER
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The speedometer output signal is generated by the PCM but my guess is the speedometer is bad though is the connections are all good. Try to remove the cluster and remove the connector then plug the connector too in to see if it was a bad connection.

Here is a video how on to do it.

https://youtu.be/_HEC44xENxw

It also shows a rebuilt cluster getting installed.

Please let us know what you find. We are interested to see what it is.

Cheers, Ken

Nov 26, 2017 at 6:54 PM