Case IH 737-05 - DEC – Transmission Control Unit (TCU): Transmission C4 clutch solenoid circuit current below normal

The transmission controller has detected an open circuit, a broken wire, a disconnected plug, or an internally failed (open) solenoid coil, preventing the proper electrical current from flowing to the C4 clutch.

• MAGNUM AFS Connect
• Case IH Magnum series (e.g., Magnum 240, Magnum 315)
• Case IH Steiger and Quadtrac series (e.g., Quadtrac 535, Steiger 620)

1. 1

   Visually inspect the C4 clutch solenoid on the transmission control valve block (typically on the right-hand side of the transmission). Check the wiring harness and electrical connector (X-041) for corrosion, pushed-out pins, or physical damage.

2. 2

   Perform a coil resistance test by disconnecting the electrical connector from the C4 clutch solenoid and measuring resistance directly at the terminals (should be 8 to 11 ohms).

3. 3

   Perform a circuit continuity test on the wiring harness between the transmission controller and the C4 solenoid connector to rule out a broken wire if the solenoid tests within specification.

1. 1

   Disconnect battery

   Disconnect the tractor's battery power before servicing the transmission electrical components.

2. 2

   Locate solenoid

   Locate the C4 clutch solenoid on the transmission control valve block.

3. 3

   Unplug connector

   Unplug the electrical connector from the C4 clutch solenoid.

4. 4

   Replace solenoid

   If the solenoid is faulty (resistance is outside the 8-11 ohm range or shows an open circuit): Remove the retaining hardware, extract the failed C4 clutch solenoid valve, and install a new replacement solenoid.

5. 5

   Repair wiring/connector

   If the wiring/connector is faulty: Cut back the damaged wire and splice in a new replacement female connector and terminal pins. Ensure the connector seal is properly seated to prevent future moisture intrusion.

6. 6

   Reconnect harness

   Reconnect the wiring harness to the solenoid.

7. 7

   Verify repair

   Reconnect battery power, start the machine, and use the diagnostic display or service tool to clear the fault codes and verify the repair.