Case IH 115 – Transmission Controller (TCU): Clutch Solenoid is shorted to +12 Volts, current sensed while driver is off

The Transmission Controller is detecting electrical current flowing through the clutch solenoid circuit even when the controller is not commanding the valve to open (the driver circuit is "off"). This means there is an unintended path to power.

• MX Magnum
• STX Steiger
• Magnum series (235–340)
• STX Steiger series
• Puma series

1. 1

   Perform a resistance test on the solenoid coil (expected: 10.3 to 12.7 ohms at 80°F / 27°C; 11.7 to 14.3 ohms at 140°F / 60°C). Lower resistance indicates a shorted coil.

2. 2

   Perform a voltage/harness test with the solenoid disconnected, key switch ON, and accessories ON. Check for voltage at the transmission controller connector cavity for the solenoid (expected: zero voltage).

1. 1

   Locate components

   Turn off the tractor and locate the transmission controller (often located underneath the fuse/relay panel in the cab) and the specific clutch solenoid on the transmission valve body.

2. 2

   Disconnect harness

   Disconnect the wiring harness from the affected clutch solenoid.

3. 3

   Test and replace solenoid

   Perform the resistance check on the solenoid coil. If it fails the resistance test (reads too low/shorted), replace the clutch solenoid valve.

4. 4

   Test and repair harness

   If the solenoid tests within spec, perform the voltage test on the harness. If voltage is found on the circuit while the key is on and the driver is off, trace the wiring harness back to the transmission controller, locate the chafed/shorted wire, and repair the harness.

5. 5

   Replace controller

   If both the solenoid and the wiring harness test perfectly fine, the transmission controller has failed internally and must be replaced.

6. 6

   Verify repair

   After repairs, clear the fault codes via the cab display. Start and drive the tractor through the forward/reverse gears to verify the code does not return. (Note: If the transmission controller is replaced, a full transmission calibration procedure must be performed).