Posted 5/12/2022 16:02 (#9657845 - in reply to #9656471) Subject: RE: Trimble Fault 42
Autopilot system fault code 42 "Man Ovrd Undervolt"
A critical Autopilot system fault has occurred. This error occurs when the voltage from the manual override sensor is
sampled at a value less than 0.3 volts. This can be caused by a faulty cable, a defective manual override sensor, or an
incorrect vehicle profile.
Note – If this is a very intermittent problem, use the display to clear the controller fault and continue to operate.
1. Check all connections, including at the sensor, to ensure that all pins are locked into place in the connector.
Check continuity from one end of a cable to the other.
– Nav I cables (P/N 41378 and P/N 49918) (wheeled tractors):
– Pin A, Gnd, J1-5
– Pin B, Signal, J1-1
– Pin C, +5.0V out, J1-12
– Nav I cables (P/N 43753 (Cat hydraulic) and P/N 49959 ( flow switch)):
– Pin A, Gnd, J1-5
– Pin B, +5V, J1-12
– Pin C, Signal, J1-1
– NavController II /NavController III cables (P/N 54618 and P/N 54626). For cable schematics, see Chapter
– P2-A, Gnd, P1-3
– P2-B, +5V, P1-2
– P2-C, Signal, P1-1
Note – Cable P/N 54626 includes a 10 k Ohm ¼ watt resistor in the pin 1 or A wire. If the resistor has failed, it will
cause Fault 42.
2. If the vehicle uses a flow switch with cable P/N 54626, verify that there is at least constant 0.3 volts. If 0.3 volts
are not present, then check the Pin 1 or A wire for the resistance shown in the previous note.
3. If the vehicle uses a flow switch for manual override, you may need to remove the flow switch to test its
a. Inspect the flow switch to ensure all mechanical parts are functioning.
b. Check the continuity between pins B and C while observing the flow, to verify the flow switch is operating
correctly. There should be continuity between pins A and C with no flow.
c. If the switch fails the continuity check or resistance test, replace the cable harness.
4. If necessary, replace the pressure transducer or flow switch.
5. Use either the Autopilot Toolbox II software or the FieldManager display to verify that the correct vehicle is
selected. Reload or select the vehicle profile that is required for the vehicle