What could be the cause of speedometer error in a 1992 Accord? An indicated 65 mph is dead on 55 mph according to a known accurate GPS.

 

wrong tires, wheels, sensor, aftermarket tweaking done wrong, pin on the speedo set wrong, etc.

 

Sorry I wasn't more specific .. this particular vehicle has original wheels, Michelin Harmony® P185/70R14 tires. No work has been performed on speedo or instrument cluster. No suspension mods or tweaking.

 

More info...speedo is accurate up to 35 MPH... error increases up to an indicated 65 mph (really 55 mph). Also an indicated 70 is actually 62, thereafter the percentage difference increase from indicated versus actual is very small. Speedo consistently shows ~ 20% error after an indicated 65 mph. Would a worn Vehicle Speed Sensor (VSS) present itself this way? No other symptoms of a failed or failing VSS exist.

 

Sounds strange .... maybe VSS or a computer thing that's not reading the sensor voltage right.