Massey Ferguson T4172 – Transmission Control Module: Transmission filter blockage switch (Sensor X20) or Transmission Oil Temperature Signal Issue

The controller is receiving an electrical reading that is out of the expected range (e.g., an open circuit, short to ground, or short to power) for either the Transmission filter blockage switch (Sensor X20) or the Transmission hydraulic oil temperature sensor (Sensor X19).

• 7622
• Interim Tier 4 (2012-2015)
• 7614
• 7615
• 7620
• 7616
• 7618
• 7619
• 7626
• 7624
• 8650
• 8670
• 8690

1. 1

   Verify the Component: Check the tractor's dash display or use an AGCO diagnostic tool to confirm whether the code is pointing to Sensor X19 (Temperature) or Sensor X20 (Filter Blockage).

2. 2

   Inspect the Wiring Harness: Visually inspect the wiring leading to the sensor. Look for chafed wires, melted insulation, or damage from field debris.

3. 3

   Check the Connector: Disconnect the sensor and inspect the pins for corrosion, moisture ingress, or pushed-back terminals.

4. 4

   Test the Circuit: Use a multimeter to verify that the sensor is receiving the correct reference voltage (usually 5V or 8.5V depending on the circuit) and has a good ground.

5. 5

   Check Fluid and Filters: Even though this is a "signal" error, ensure the transmission fluid is at the correct level and the transmission oil filter is not severely clogged, as extreme bypass conditions can sometimes cause erratic switch behavior.

1. 1

   Prepare the tractor

   Park the tractor on a level surface, engage the parking brake, lower all implements, and turn off the engine.

2. 2

   Locate the faulty sensor

   Locate the faulty sensor on the transmission housing: Filter Blockage Switch (X20) is typically located on or immediately adjacent to the transmission hydraulic oil filter housing. Oil Temperature Sensor (X19) is generally located on the transmission sump or main hydraulic valve block.

3. 3

   Clean the area

   Thoroughly clean the area around the sensor with brake cleaner or a rag to prevent dirt from entering the transmission system.

4. 4

   Prepare for fluid loss

   Place a clean drain pan underneath the sensor location, as a small amount of transmission/hydraulic fluid will escape when the sensor is removed.

5. 5

   Disconnect harness

   Disconnect the electrical harness from the sensor.

6. 6

   Remove faulty sensor

   Using a deep socket or wrench, carefully unscrew the faulty sensor.

7. 7

   Install new sensor

   Install the new sensor. If the new sensor does not have a pre-installed O-ring or pre-applied thread sealant, apply a hydraulic-safe thread sealant. Torque to OEM specifications.

8. 8

   Reconnect harness

   Reconnect the electrical harness, ensuring it clicks securely into place.

9. 9

   Check fluid level

   Check the transmission fluid level and top up if necessary.

10. 10

    Test and clear code

    Start the tractor, check the sensor area for leaks, and clear the fault code using a diagnostic tool (or verify it clears actively upon startup).