Case IH 42 – Transmission Control Module (TCM): Forward solenoid coil open circuit

The control module has detected a break in the electrical circuit (infinite or excessively high resistance) controlling the forward directional solenoid. When this occurs, the transmission cannot engage the forward clutch pack, and the tractor will typically lose forward propulsion (often flashing the neutral light or throwing the tractor into a neutral state).

• MX Maxxum
• MX80C
• MX90C
• MX100
• MX100C
• MX110
• MX120
• MX135
• MX150
• MX170
• CX50
• CX60
• CX70
• CX80
• CX90
• CX100

1. 1

   Locate the Shuttle Valve Block: On the MX series, the forward/reverse shuttle valve block typically houses 4 identical solenoids. The standard layout is: Left-Rear = Forward, Left-Front = Reverse, Right-Rear = Diff Lock, Right-Front = MFD (Mechanical Front Wheel Drive).

2. 2

   Ohm Test the Coil: Disconnect the electrical harness from the Forward solenoid (left rear). Using a digital multimeter, measure the resistance across the two pins on the solenoid coil. A healthy OEM coil should test between 8 to 10 ohms.

3. 3

   Evaluate the Reading: If the multimeter reads 'OL' (Open Loop) or a significantly higher resistance, the internal coil winding is broken and the solenoid must be replaced.

4. 4

   Check the Harness: If the coil tests within the 8-10 ohm spec, the open circuit is in the tractor's wiring. Inspect the harness for rubbed-through insulation, broken wires, or heavy rust/corrosion inside the connector plug (a highly common failure point on these models).

5. 5

   Bypass Test (Optional): You can temporarily swap the Forward solenoid coil with the Reverse or Diff Lock coil (since they are the same part number) to see if the fault code changes or if forward drive is restored.

1. 1

   Park and secure tractor

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

2. 2

   Disconnect battery

   Disconnect the negative battery cable to prevent electrical shorts.

3. 3

   Locate and clean valve assembly

   Locate the Forward/Reverse shuttle valve assembly on the transmission housing. Clean the area around the valve block thoroughly to prevent dirt from entering the hydraulic system.

4. 4

   Disconnect electrical plug

   Disconnect the electrical plug from the Forward solenoid (left rear position).

5. 5

   Remove retaining nut

   Remove the retaining nut at the end of the solenoid stem.

6. 6

   Remove faulty coil

   Slide the faulty solenoid coil off the valve cartridge. (Caution: If you need to remove the entire valve cartridge rather than just the coil, be prepared to catch the internal spool, as it can fall out).

7. 7

   Install new coil

   Slide the new solenoid coil onto the valve stem and tighten the retaining nut.

8. 8

   Apply dielectric grease and reconnect

   Apply a small amount of dielectric grease to the electrical connector to prevent future corrosion, and plug it back into the solenoid.

9. 9

   Verify repair

   Reconnect the battery, start the tractor, and shift into forward to verify that the code has cleared and engagement is restored.