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RussMasterTech, ASE Certified Technician
Category: GM
Satisfied Customers: 791
Experience:  19 years of GM Dealership experience. ASE Master with L1 and GM Master Certified in Electrical
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2000 gmc: speedometer..instrument..mechanic friend..diagnostic test

Resolved Question:

The speedometer on my 2000 gmc savana cargo van isn 't working. SPECMO says the instrument in the dash checks out good. A mechanic friend ran a diagnostic test on the engine and said the computer is reading the speed. What could it be?
Submitted: 7 years ago.
Category: GM
Expert:  RussMasterTech replied 7 years ago.



If the green wire between the VCM/PCM is shorted to ground or power, the speed signal would not be received by the IPC. I'll send you the schematic. There's not much else it could be if the VCM is seeing the signal. Either the wire is damaged between the VCM and the IPC or the VCM is defective. There are a lot of problems with corrosion on those VCM's.


Here's the schematic.


Object Number: 521734  Size: FS

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