Case IH tAC – PCU (Power Control Unit / Powertrain Control Unit): PCU CAN Bus Off, Data Valid But Above Normal Range

This code indicates a communication failure on the Controller Area Network (CAN) bus specifically related to the PCU. The system is receiving valid data, but the values fall above the expected normal operating range, causing the PCU to drop offline ("Bus Off") to protect the network or due to signal corruption.

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190
• TM115
• TM125
• TM135
• TM150
• TM165

1. 1

   Check for accompanying codes such as tAD, tAE, or tAF to isolate if the issue is a physical short or a module failure

2. 2

   Inspect the CAN bus wiring harness leading to the PCU for chafing, bare wires, or pinched sections

3. 3

   Disconnect the PCU and check the pins for corrosion, moisture, or pushed-back terminals

4. 4

   Verify that the PCU is receiving proper operating voltage and has a clean ground connection

1. 1

   Repair Wiring

   If a short or open circuit is found in the CAN bus wiring during diagnostics, repair the damaged section or replace the affected harness segment.

2. 2

   Replace PCU

   If the wiring, power, and grounds are intact but the PCU fails to communicate on the CAN bus, the PCU itself must be replaced.

3. 3

   Perform Transmission/EDC Calibration

   Lower all equipment to the ground. Place all shift levers in neutral. Block the wheels (front and rear) to prevent unexpected tractor movement. Press and hold the High and Low range buttons simultaneously and start the engine. When 'CAL' appears in the transmission display, release the High and Low range buttons. Set the engine speed to 1200 RPM (± 100 RPM). Follow the on-screen prompts to complete the clutch and synchronizer calibration.