New Holland T8010 Manual page 1562

Locate the transmission speed sensor on top of the transmission.
Disconnect connector C069 from the sensor.
Inspect the connector. Clean the connection.
Measure the sensor resistance between pin A and Pin B.
The resistance should be around 3 k ohms at 20 degree Celsius.
If the resistance is not in the specified range, replace the transmission speed sensor.
NOTE: There are cases where the resistance of the sensor is within the specified range but its signal may not be
right. To verify the validity of the speed signal is a complicated process. If it is suspected that the signal may be
wrong, replace the transmission speed sensor
7. Test engine speed sensing (refer to the troubleshooting procedure for fault 79)
If the tractor has engine controller, refer to engine diagnosing procedures for troubleshooting.
If the tractor does not have engine controller, do the following:
A. Make sure the alternator is the correct model. Incorrect alternator will give wrong signal frequency which
may trigger this fault code.
B. Check for worn alternator belt.
C. Check the Engine RPM signal wiring.
D. Check the Engine RPM signal at terminal W of the alternator.
Section 55 - Electrical System, Controller - Chapter 4
55-4-35