Massey Ferguson X122 – Armrest / Dash: Hand Throttle Circuit Fault

The fault code X122 indicates an electrical problem with the hand throttle control circuit. The specific nature of the fault varies by prefix: D 170 / D 175 indicate a general or open circuit logged by the Dash, AR 72 indicates a short circuit to 12V logged by the Armrest, and AR 81 indicates a short circuit to 0V (ground) logged by the Armrest.

• 8600 Series
• 8650
• 8660
• 8670
• 8680
• 8690
• 6700R Series
• 5600 Series
• 6600 Series
• 7600 Series
• 4707
• 7700S Series

1. 1

   Inspect the wiring harness and connectors between the hand throttle sensor and the armrest control module for damage, corrosion, or loose connections

2. 2

   Verify battery voltage is stable (12.6V fully charged, 13.8V-14.2V running) and check relevant fuses for the armrest controller

3. 3

   Test the Throttle Position Sensor (TPS) with a multimeter: verify a stable 5V reference on the power wire and a good ground connection

4. 4

   Measure the TPS signal wire voltage while moving the hand throttle through its full range; look for smooth changes without sudden spikes or dropouts

1. 1

   Isolate the fault

   Based on diagnostic checks, determine if the issue is isolated to the sensor, the wiring harness, or the control module.

2. 2

   Repair wiring

   Repair or replace any damaged wiring or connectors found during inspection. Ensure all connections are clean and secure.

3. 3

   Replace sensor or assembly

   If the throttle position sensor fails the multimeter test (shows voltage glitches or dropouts), replace the sensor or the complete hand throttle lever assembly.

4. 4

   Calibrate hand throttle

   Put the tractor into calibration mode and move the throttle lever to its minimum and maximum positions to teach the control module the new sensor's range. This may require the AGCO EDT diagnostic tool on newer models.