Case IH tCF – PCU (Power Control Unit): 1 CAN Chip, Shorted To High Source

This indicates a critical electrical issue where the Controller Area Network (CAN) bus chip 1 is detecting a short circuit to a high voltage source (typically battery voltage).

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Inspect the CAN bus wiring harness connected to the PCU for any chafing, melted insulation, or pinched wires that could cause a short to a high voltage source (battery power)

2. 2

   Disconnect the PCU and check the pins for corrosion, moisture, or bridging that could cause a short circuit

3. 3

   If the wiring harness tests intact with no shorts to power, isolate the controller as the internal CAN chip within the PCU has likely failed

1. 1

   Resolve the Short

   Repair or replace any damaged sections of the CAN wiring harness. If the wiring is good, replace the PCU/Transmission Controller.

2. 2

   Post-Repair Calibration

   If the microprocessor/controller is replaced, or if the non-volatile memory has been reset, a Transmission/EDC Calibration is strictly required.

3. 3

   Calibration Setup

   Connect the diagnostic switch (Special Tool No. 380000488) into the black diagnostic socket (for Dual Command and Range Command models) or the white socket depending on your specific transmission. Block the wheels (front and rear) and lower all equipment to the ground. Place all shift levers in neutral.

4. 4

   Run Calibration

   Hold the High and Low range buttons and start the engine. Release the buttons when ''CAL'' appears in the transmission display. Set the engine speed to 1200 ERPM (± 100). Follow the H-Menu prompts to calibrate the clutches. Hold the range buttons until ''SOC'' appears during calibration. The display will show ''END'' to signify successful completion.