Case IH 45 – Transmission Control Unit (TCU): Reverse solenoid coil open circuit

The controller has commanded the reverse solenoid to energize, but it detects zero or insufficient current draw (typically under 13 mA or 250 mA). This indicates an open circuit, usually caused by a burned-out solenoid coil, a severed wire, a disconnected plug, or a failed relay, resulting in the tractor failing to engage reverse gear.

• MX Maxxum
• Magnum Series: MX180 through MX285, 225, 250, 310, 7120
• Maxxum Series: 5120, 5130, 5140, 5150, MX100 through MX170, 110, 120, 135
• Puma Series: 165 through 225, 170
• CX Series: CX50 through CX110
• Steiger / Quadtrac Series

1. 1

   Visually inspect the reverse solenoid wiring on the transmission control valve block for mud packing, rodent damage, or a disconnected plug.

2. 2

   Perform the 'Swap' Test: Swap the electrical connectors between the forward and reverse solenoids. If the tractor refuses to go forward but goes in reverse, the solenoid coil is dead. If the problem stays in reverse, the issue is in the wiring harness, relay, or shuttle switch.

3. 3

   Perform a Coil Resistance Test: Use a multimeter to measure the resistance across the two pins of the reverse solenoid coil. An 'OL' (Open Loop) or infinite resistance reading confirms the coil has an internal open circuit.

4. 4

   Perform a Voltage Check: Turn the key ON and move the shuttle lever to reverse. Check for voltage (approximately 11-12V) at the harness plug. If voltage is missing, check the forward/reverse relays in the right-hand dash/console.

5. 5

   Check the Shuttle Switch: Ensure the magnetic neutral switch on the shift rods or the shuttle lever toggle switch is functioning and clicking properly.

1. 1

   Park tractor

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

2. 2

   Locate solenoid

   Locate the reverse solenoid on the transmission control valve block (refer to your specific model's service manual for exact LH/RH side placement).

3. 3

   Clean area

   Thoroughly clean the area around the solenoid to prevent dirt from entering the transmission valve body.

4. 4

   Disconnect connector

   Disconnect the 2-pin electrical connector from the reverse solenoid.

5. 5

   Remove retaining nut

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

6. 6

   Remove faulty coil

   Slide the faulty solenoid coil off the valve cartridge stem. (Note: You usually do not need to remove the hydraulic valve cartridge itself, just the electromagnetic coil, which prevents fluid loss).

7. 7

   Install new coil

   Slide the new OEM solenoid coil onto the stem and secure it with the retaining nut.

8. 8

   Reconnect wiring

   Reconnect the wiring harness plug. Ensure it clicks into place securely.

9. 9

   Clear codes and test

   Clear the fault codes from the TCU via the diagnostic menu and test the shuttle shift operation in reverse.