Case IH 734-01 - DEC – Transmission Controller (TCU): Transmission C1 clutch solenoid electrical circuit fault voltage low

The transmission controller has detected that the voltage in the electrical circuit for the C1 clutch solenoid has dropped below the acceptable operating threshold. This is typically caused by low overall system voltage, a short to ground in the wiring harness, a bad ground connection, or an open circuit.

• MAGNUM AFS Connect
• Magnum Series Tractors
• MX210
• MX230
• MX255
• MX285
• TG series tractors

1. 1

   Test battery voltage to ensure it is between 12 and 14 volts (if multiple low-voltage codes exist, the battery or alternator is likely the culprit)

2. 2

   Check the system voltage at pin 14 of connector C350 on the transmission controller

3. 3

   Inspect for bad connections and improper grounds at cavities 19, 23, 25, and 26 of connector C350

4. 4

   Remove the controller cover from the rear of the tractor and visually inspect the wiring harness running from the transmission controller towards the solenoids under the cab for physical damage, chafing, or shorts to ground

5. 5

   Disconnect connectors C350 and C353 from the transmission controller and measure the resistance between cavity 9 of connector C350 and cavity 8 of connector C353 on the wiring harness side (should be around 10 ohms)

1. 1

   Preparation

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

2. 2

   Access the Controller

   Remove the controller cover at the rear of the tractor to access the Transmission Controller.

3. 3

   Perform Wiring Repairs

   If the resistance test fails or physical damage is found, trace the harness from the TCU to the C1 Clutch Solenoid (identified as Connector No. 31 in the schematic). Repair any broken wires or shorts to ground.

4. 4

   Access the Solenoid

   If the wiring tests perfectly, the C1 clutch solenoid itself has likely failed internally. Locate the transmission powershift valve block under the cab.

5. 5

   Remove the Solenoid

   Disconnect Connector No. 31 from the C1 clutch solenoid. Remove the retaining hardware securing the solenoid to the valve block and carefully extract the solenoid.

6. 6

   Install the New Solenoid

   Lubricate the new O-rings/seals with clean transmission fluid. Insert the new C1 clutch solenoid into the valve block and tighten the retaining hardware to OEM torque specifications.

7. 7

   Reassembly

   Reconnect Connector No. 31. Reinstall the transmission controller cover.

8. 8

   Testing

   Reconnect the battery. Start the tractor, clear the stored fault codes, and cycle the transmission through its gears to ensure the C1 clutch engages properly and the code does not return.