Case IH FBC – Transmission Controller (TCU): Clutch C Solenoid Over Voltage

The control module has detected a short circuit to +12 volts on the Clutch C solenoid circuit, or that electrical current is still being measured when the solenoid driver is commanded off.

• MXM
• MXM120
• MXM130
• MXM140
• MXM155
• MXM175
• MXM190

1. 1

   Inspect the wiring harness running from the Transmission Controller to the transmission valve block. Look for chafed, melted, or pinched wires that could be causing a short to +12V.

2. 2

   Disconnect the Clutch C solenoid and inspect the connector pins for corrosion, moisture, or damage that could bridge the circuits.

3. 3

   Measure the resistance across the Clutch C solenoid terminals. An internal short within the solenoid coil is a common cause for the over-voltage/current-sensed condition.

4. 4

   With the tractor on but the drive disengaged, probe the solenoid connector to verify if +12V is improperly present when the controller is commanding the clutch off.

1. 1

   Safely park the tractor on level ground, engage the parking brake, and turn off the engine.

2. 2

   Locate the transmission control valve block where the clutch solenoids are mounted.

3. 3

   Disconnect the electrical connector specifically for the Clutch C solenoid.

4. 4

   If the diagnostic checks revealed a wiring harness short, repair the damaged section of the wire and insulate it properly.

5. 5

   If the solenoid itself failed the resistance test (internally shorted), remove the retaining hardware and extract the faulty Clutch C solenoid from the valve block.

6. 6

   Lubricate the O-rings on the new OEM solenoid with clean transmission fluid and install it into the valve block. Secure the retaining hardware.

7. 7

   Reconnect the electrical connector.

8. 8

   Recalibrate the transmission clutches.

   Hold the High and Low range buttons and start the engine. Wait for 'CAL' to appear on the transmission display, then release the buttons. Set the engine speed to 1200 RPM and follow the H-Menu prompts to calibrate the clutches.

9. 9

   Clear the stored fault codes and test drive the tractor to ensure smooth shifting through the ranges.