this is the first time I'm asking anything on this StackExchange, so I'm not sure about they right question format, so I'll get straight to the point.
I performed a Gauge Cluster Light Self-Test on my 2007 Honda Accord (CM2), and after doing this, my speedometer now shows a speed below 0. It increases accordingly when I accelerate (as normal), but if I'm actually doing around 60kph, it will show about 35kph on the speedometer.
I'm not an experienced technician, but I'd really appreciate if there was a solution I could do myself to fix this issue.
Edit: Just checked speed with a GPS, and my speedometer reading is exactly 15kms less than the actual speed shown on GPS.