Case IH 3947 – Engine Control Module (ECM): Torque or speed control demand from PTO Retarder exceeding the maximum time

This is a CAN Bus communication error. It means the continuous torque or speed control demand signal being sent from the PTO Retarder controller to the engine has exceeded the maximum allowable time limit programmed into the system.

• tractors and machinery equipped with Tier 3 and Tier 4a engines
• FPT NEF engines

1. 1

   Check the CAN cable connecting the PTO Retarder controller to the ECM for physical damage, broken wires, or short circuits in the wiring harness

2. 2

   Inspect the connectors at both the PTO Retarder controller and the ECM for corrosion, loose pins, or moisture ingress

3. 3

   Test the PTO Retarder controller for internal defects or implausible signal outputs

1. 1

   Power Down

   Turn off the machine and disconnect the battery to ensure safety while working on the CAN bus electrical system.

2. 2

   Inspect and Repair Wiring

   Trace the CAN cable from the PTO Retarder controller to the ECM. If any chafing, breaks, or shorts are found, repair the wiring harness or replace the damaged section of the CAN cable.

3. 3

   Clean Connections

   Disconnect the harnesses at the PTO Retarder controller and the ECM. Clean the contacts with electrical contact cleaner and ensure the pins are seated tightly.

4. 4

   Replace the Controller

   If the wiring and connections test good (proper continuity and no shorts to ground/power), the fault lies within the PTO Retarder controller itself. Remove the defective controller and install a new unit.

5. 5

   Clear and Test

   Reconnect the battery, connect a diagnostic tool to the machine, and clear the inactive 3947 fault code. Run the machine and engage the PTO retarder to verify the code does not return.