Case IH 5900-03 - DEC – Transmission Control Unit (TCU) or Electronic Control Module (ECM): Transmission System Pressure Control Solenoid Voltage Above Normal

The electrical circuit for the transmission system pressure control solenoid is experiencing a 'voltage above normal' condition (FMI 3). This means the controller is receiving a voltage reading on the solenoid circuit that is higher than the expected operating range, typically caused by a wiring harness shorting to a power source (battery voltage) or an internal short within the solenoid coil itself.

• MAGNUM AFS Connect
• Magnum series
• Steiger/STX series
• Puma series
• Maxxum series
• Case wheel loaders

1. 1

   Visually inspect the wiring harness connecting the TCU to the transmission pressure control solenoid for chafing, melted insulation, or pinched wires that could cause a short to a 12V or 24V power source.

2. 2

   Disconnect the solenoid connector and check for corrosion, moisture, or bent pins, which can bridge circuits.

3. 3

   Use a digital multimeter to check the voltage on the solenoid signal wire with the key ON (engine off). If it shows full battery voltage when it shouldn't, there is a short to power in the harness.

4. 4

   Measure the resistance (ohms) across the solenoid coil pins and compare it to OEM specifications. An abnormally low resistance reading indicates the solenoid is internally shorted.

1. 1

   Disconnect power

   Turn off the machine, remove the key, and disconnect the battery to prevent electrical spikes and ensure safety.

2. 2

   Locate valve block

   Locate the transmission control valve block, which is typically mounted on the side or top of the transmission housing.

3. 3

   Disconnect solenoid

   Disconnect the electrical connector from the suspect pressure control solenoid.

4. 4

   Repair wiring

   If the issue is wiring: Repair or replace the affected section of the transmission wiring harness where the short to power was found.

5. 5

   Clean valve block area

   If the issue is the solenoid: Clean the area around the valve block thoroughly to prevent dirt or debris from entering the transmission hydraulic system.

6. 6

   Remove faulty solenoid

   Unbolt and remove the faulty solenoid valve (be prepared to catch a small amount of hydraulic fluid with a drain pan).

7. 7

   Install new solenoid

   Lubricate the O-rings on the new solenoid with clean hydraulic fluid and carefully install it into the valve block.

8. 8

   Torque and reconnect

   Torque the retaining bolts to OEM specifications and reconnect the electrical harness.

9. 9

   Test machine

   Reconnect the battery, start the tractor, and clear the fault codes via the cab display or diagnostic tool. Test the transmission through its gears to verify the repair and ensure smooth shifting.