I would suspect speed sensor
check for codes scan speed as you are driving does it show the same as the cluster ??
VEHICLE SPEED SENSOR
The vehicle speed sensor uses a Hall IC pick-up to generate speed signals. (MT models)
This sensor is installed on the transmission case and detects rotating speed of the transmission output gear.
The sensor generates 4 pulses per rotation of the speed sensor driven shaft and send them to the speedometer.
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