Massey Ferguson AR42 – TECU (Transmission Electronic Control Unit): High Voltage On Auxiliary Valve Switch 4 (TECU) / FingerTIP 4 - Short circuit to 12 V

The system has detected that the voltage signal coming from the FingerTIP 4 switch (which controls the 4th auxiliary/spool valve) is too high. This typically indicates that the signal wire is shorted directly to a 12V power source, or the switch/potentiometer itself has failed internally and is passing full voltage.

• 7616
• 5612
• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 5611
• 7615
• 5610
• 5613
• 7620
• 5609
• 7618
• 5608
• 7619
• 7626
• 7624
• 5400 Series
• 6400 Series
• 7400 Series
• 7600 Series
• 7700 Series
• 8400 Series
• 8600 Series
• Dyna-4
• Dyna-6
• Dyna-VT

1. 1

   Inspect the FingerTIP 4 switch connector (X588 or X109) inside the armrest console for bent pins, corrosion, or moisture.

2. 2

   Check the signal wire from the FingerTIP 4 switch to the TECU for a short circuit to 12V (battery voltage), paying special attention to the wiring harness where it routes through the armrest pivot point for chafing.

3. 3

   Verify that the TECU is supplying the correct 10V reference voltage to the armrest module and that it is not spiking.

4. 4

   Test the FingerTIP 4 potentiometer/switch for internal shorts by checking if the resistance sweeps erratically or shows a dead short to the power pin.

5. 5

   Rule out a failed calibration (though code AR49 usually flags incomplete calibration, ensure the issue is a hardware short and not a calibration error).

1. 1

   Disconnect Power

   Disconnect the tractor's battery to prevent electrical spikes during the repair.

2. 2

   Access the Armrest

   Remove the cladding/screws securing the top panel of the armrest console to expose the FingerTIP joystick and switch modules.

3. 3

   Disconnect the Switch

   Locate the FingerTIP 4 switch (Auxiliary Valve Switch 4) and disconnect its wiring harness (X588/X109).

4. 4

   Replace the Component

   If diagnostic tests proved the switch was internally shorted, remove the retaining hardware (usually small Torx or Phillips screws and a spring nut) and remove the faulty switch/potentiometer. Install the new OEM switch.

5. 5

   Reassemble

   Reconnect the wiring harness, ensuring the connector clicks securely into place. Reinstall the armrest console panels.

6. 6

   Reconnect Power & Clear Codes

   Reconnect the battery. Turn the ignition on and clear the error code from the instrument panel/control unit.

7. 7

   Calibrate

   You must perform a calibration of the auxiliary valve switches. This is typically done through the Datatronic screen/diagnostic menu or by a dealer using the EDT (Electronic Diagnostic Tool).