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What else, other then the VSS, tells the computer how fast the car is going, or, what could be causing the VSS to think the car is going faster then it is?

VSS has been replaced w/new AC Delco unit and computer still sees 20-30 mph faster then actual when warmed up. Before running for around 10-15 min. everything is fine.

Thanks dunno
 

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Fuhgeddaboudit
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Transmission speedometer gear and rear tire size has effect on it also. But the after heating up has me dunno Check voltage at ecm and alternator. Spikes can cause weird problems.
 

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The VSS is driven by the speedo cable, and the ECM has ONLY the VSS signal to indicate vehicle speed. If the relationship between VSS output and vehicle speed is not constant, it must be an electrical problem. Bad ground, maybe? Have to look at that circuit and see what is involved.
 
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