Massey Ferguson D198 – Instrument Panel Control Unit: Auxiliary Hydraulic Oil Temperature Sensor - Electrical signal is too low

The electrical signal from the Auxiliary Hydraulic Oil Temperature Sensor (Component X1) is too low. This condition is typically caused by a short circuit to ground in the sensor's wiring harness or a complete internal failure of the sensor itself.

• MF 8600
• MF 8650
• MF 8660
• MF 8670
• MF 8680
• MF 8690
• MF 8450
• MF 8460
• MF 8470
• MF 8480
• 8600 Series
• 7600 Series
• MF 7614 to 7618
• 8400 Series

1. 1

   Inspect the wiring harness connected to the Auxiliary Hydraulic Oil Temperature Sensor (Sensor X1).

2. 2

   Check the circuit wire running from terminal 67 of the DCC2 controller for a short to ground, as this wire is prone to shorting.

3. 3

   Disconnect the sensor and check the plug for hydraulic oil intrusion, corrosion, or backed-out pins.

4. 4

   Measure the resistance across the sensor's terminals with a multimeter. If it reads completely open or dead shorted, the sensor has failed.

1. 1

   Prep the Machine

   Park the tractor on a level surface, lower all hydraulic implements, turn off the engine, and disconnect the battery.

2. 2

   Locate the Sensor

   Locate Sensor X1 (Auxiliary Hydraulic Oil Temperature Sensor) on the auxiliary hydraulic valve block.

3. 3

   Disconnect and Isolate

   Unplug the electrical connector. If your diagnostic checks revealed a short in the harness (e.g., terminal 67 wire), repair the chafed/damaged wire using heat-shrink connectors and re-loom the harness.

4. 4

   Remove the Sensor

   If the wiring is intact, the sensor must be replaced. Place a clean catch pan under the sensor area to catch any residual hydraulic fluid. Unscrew the faulty sensor.

5. 5

   Install the New Part

   Thread the new temperature sensor into the hydraulic block. Tighten to the specified torque (do not over-tighten, as this can crack the brass housing).

6. 6

   Reassemble

   Reconnect the electrical harness to the new sensor.

7. 7

   Clear Codes

   Reconnect the battery, turn the key to the ON position, and use the Instrument Panel Control Unit to verify the D198 code has moved from 'Active' to 'Stored' or has cleared entirely. Top off the hydraulic fluid if any was lost during the swap.