Case IH 48 – Transmission Controller (TCU / Trans / ATC): Bottom of Clutch (BOC) pedal switch or the bottom of clutch relay (neutral relay) are short circuit.

The controller is detecting a continuous closed circuit (voltage or ground) in the BOC switch or relay circuit when it expects an open circuit. This usually means the switch is internally shorted, the relay is stuck closed, or the wiring harness has shorted to another power or ground wire.

• MX Magnum
• STX Steiger
• Magnum series (MX, TG, and Series 4 235-340)
• Maxxum series
• Puma series
• Steiger tractors

1. 1

   Verify the mechanical adjustment of the clutch (inching) pedal stop and the BOC switch. The switch should actuate (click) when the pedal is being raised, ideally between 8% and 14% of the pedal's travel.

2. 2

   Disconnect the BOC switch at the base of the clutch pedal and use a multimeter to check for an internal short. If the switch shows continuity when it should be open, the switch is faulty.

3. 3

   Locate the Neutral Relay (Bottom of Clutch Relay) in the cab fuse/relay panel and swap it with a known good relay of the same type to see if the fault clears.

4. 4

   Inspect the wiring harness between the BOC switch, the neutral relay, and the transmission controller for chafed wires, melted insulation, or pinched harnesses that could cause a short circuit to ground or 12V power.

1. 1

   Power Down

   Turn off the tractor, remove the key, and locate the BOC switch at the base of the clutch pedal assembly inside the cab.

2. 2

   Replace the Switch (if faulty)

   Unplug the electrical connector from the BOC switch. Unbolt the switch bracket or unscrew the switch from its mounting point. Install the new switch.

3. 3

   Replace the Relay (if faulty)

   Access the main fuse/relay panel. Pull the faulty Neutral Relay and replace it with a new one.

4. 4

   Repair Wiring (if applicable)

   If the switch and relay test fine, trace the circuit wires. Splice and heat-shrink any damaged sections of the wiring harness causing the short.

5. 5

   Adjust the Switch

   Once installed, adjust the BOC switch so that it properly opens and closes within the 2% to 12% range of the pedal's calibrated travel. You should hear an audible click as the pedal is depressed to the floor and released.

6. 6

   Calibrate and Clear

   Turn the key on and use the tractor's electronic service tool or H-Menu diagnostic screen to clear the fault codes. Perform a clutch pedal calibration procedure to ensure the Transmission Controller learns the new switch's engagement points.

7. 7

   Test Drive

   Test the tractor's forward/reverse shuttle operation to confirm the transmission engages properly and the code does not return.