Case IH 735-16 - DEC – Transmission Control Unit (TCU) / Drivetrain Electronic Controller (DEC): Transmission C2 clutch solenoid electrical circuit fault voltage high

The transmission controller has detected an abnormally high voltage on the electrical circuit controlling the C2 clutch solenoid, indicating a short to a 12-volt power source or an internal short within the solenoid coil. This prevents proper regulation of the C2 clutch and may result in the transmission defaulting to a Limp Home Mode, limiting vehicle speed, or locking out certain gears.

• MAGNUM AFS Connect
• Case IH Maxxum series (5120, 5130, 5140, 5150)
• Case IH Magnum series

1. 1

   Park the machine on firm ground, apply the parking brake, and shut down the engine before beginning diagnostics.

2. 2

   Inspect the wiring harness running from the Transmission ECU to the C2 clutch solenoid for rubbed-through insulation that could cause a short to a 12V power wire.

3. 3

   Disconnect the electrical connector at the C2 clutch solenoid and check for water ingress, corrosion, or bent pins.

4. 4

   Perform a voltage test to check for a harness short: With the key ON (engine off), use a multimeter to probe the harness side of the connector. If it reads +12V constantly when the driver circuit should be off, the harness is shorted to power.

5. 5

   Perform a solenoid resistance test to check for an internal short: Measure the resistance across the pins of the C2 clutch solenoid. If the resistance is near zero, the solenoid is internally shorted and must be replaced.

1. 1

   Preparation

   Clean the area around the transmission valve block thoroughly to prevent dirt from entering the hydraulic system.

2. 2

   Disconnect

   Unplug the electrical connector from the C2 clutch solenoid.

3. 3

   Removal

   Remove the retaining clip or bracket holding the C1/C2 blocking solenoids in place. Carefully pull the C2 clutch solenoid free from the valve body.

4. 4

   Installation

   Coat the O-rings of the new C2 clutch solenoid with clean transmission fluid or petroleum jelly (vaseline). Seat the new solenoid squarely into the bore and reinstall the retaining bracket/clip.

5. 5

   Reconnect

   Plug the electrical connector back into the solenoid. If the connector housing is damaged, splice in a new pigtail/connector.

6. 6

   Calibration

   After replacing the solenoid or repairing the wiring, clear the fault codes from the TCU. You must then perform a transmission clutch calibration procedure (often requiring the tractor to be at operating temperature) so the controller can learn the fill times for the new C2 clutch solenoid.