Massey Ferguson P42 – TRANS1: Hydraulic Trailer Brake Solenoid Issue

Short circuit to earth (-) on the Trailer brake safety solenoid valve (X39). The controller has detected that the electrical circuit for the trailer brake safety solenoid is shorting out to the ground, preventing the valve from operating correctly.

• 7614
• 7615
• 7616
• 7618
• 7619
• 7620
• 7622
• 7624
• 7626
• Interim Tier 4 (2012-2015)
• 6600 Series
• 6614
• 6615
• 6616
• 7600 Series
• 7700 Series
• 7715
• 7716
• 7718
• 7719
• 7720
• 7722
• 7724
• 7726
• 8600 Series
• 8670
• 8690
• 8S Series
• 8S.205
• 8S.225
• 8S.245
• 8S.265

1. 1

   Locate the Trailer Braking Safety Solenoid Valve (X39) on the transmission/hydraulic control block.

2. 2

   Visually inspect the wiring harness from the X39 solenoid back to the TRANS1 module for pinched wires, melted insulation, or rubbing against the chassis.

3. 3

   Test the solenoid coil by disconnecting the electrical connector and measuring resistance across the pins and to the solenoid body (ground). Continuity to ground indicates an internally shorted coil.

4. 4

   Test the harness for a short to ground with the solenoid disconnected and the key ON to determine if the issue is in the wiring rather than the solenoid.

1. 1

   Power Down

   Turn off the tractor, remove the key, and disconnect the battery to prevent electrical spikes.

2. 2

   Relieve Pressure

   Ensure all hydraulic pressure in the trailer braking circuit is relieved by pumping the brake pedals a few times.

3. 3

   Remove the Solenoid

   Disconnect the electrical connector from the X39 Trailer Braking Safety Solenoid. Depending on the valve block design, either remove the retaining nut to slide the electromagnetic coil off the valve stem, or unscrew the entire cartridge valve from the hydraulic block.

4. 4

   Repair Wiring (If Applicable)

   If the diagnostic checks revealed a chafed wire shorting to the chassis, splice and repair the damaged wire, then wrap it in a protective wire loom.

5. 5

   Install New Solenoid

   Slide the new solenoid coil onto the valve stem (or thread the new cartridge valve into the block) and tighten to OEM torque specifications.

6. 6

   Reassembly

   Reconnect the electrical connector and reconnect the battery.

7. 7

   Clear Codes and Test

   Use a diagnostic tool to clear the P42 fault code from the TRANS1 module. Start the tractor and test the hydraulic trailer brakes to ensure the code does not return and the brakes engage/disengage properly.