Massey Ferguson T166 – TRANS1: Brake Pressure Sensor High Volts Dyna 6 (TRANS1) / Brake sensor 50 km/h (31 mile/h) Short circuit to +12 V.

The system is detecting a high voltage signal (short circuit to +12V) from the high-pressure brake sensor (Component X495). Symptom: No drop in pressure despite braking.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• 6465
• 6475
• 6480
• 7465
• 7475
• 7480
• 8650
• 8660
• 8670
• MF 5400 Series

1. 1

   Inspect the wiring harness leading from the TRANS1 module to the X495 brake pressure sensor for chafed wires that may be causing a short circuit to a +12V power source.

2. 2

   Disconnect the sensor and inspect the pins for corrosion, water ingress, or bent terminals.

3. 3

   With a multimeter, verify the reference voltage and signal return at the sensor connector to confirm if the short to +12V is originating in the harness or if the sensor itself has failed internally.

1. 1

   Power Down

   Turn off the tractor and disconnect the battery to prevent electrical spikes during repair.

2. 2

   Locate the Sensor

   Locate the X495 brake pressure sensor on the high-pressure braking unit / air supply system.

3. 3

   Repair Wiring

   If the diagnostic checks revealed a short to +12V in the harness, repair the damaged section of the wire and apply heat shrink/loom to protect it.

4. 4

   Replace the Sensor

   If the wiring tests good, the sensor has failed internally. Unplug the electrical connector, unthread the old sensor from the brake/air supply port, and install the new sensor.

5. 5

   Reassemble and Clear Codes

   Reconnect the battery, turn the key to the ON position, and use a diagnostic tool to clear the T166 / 14.00.0A fault code from the TRANS1 module.

6. 6

   Test Operation

   Start the tractor and test the brakes. Verify via the diagnostic tool or dash that the brake pressure drops appropriately when the brakes are applied.