Case IH 3946 – Engine Control Module (ECM) / EDC: Continuous negative torque control demand from Driveline Retarder exceeding the maximum time.

This condition occurs when the Driveline Retarder continuously broadcasts a request for negative torque (engine braking/torque reduction) over the CAN bus for a duration that exceeds the programmed maximum time limit allowed by the engine's software.

• Case IH equipment with FPT Tier 3 and Tier 4a diesel engines
• CNH Industrial equipment with FPT Tier 3 and Tier 4a diesel engines

1. 1

   Check the CAN bus communication network between the Driveline Retarder controller and the Engine ECM

2. 2

   Inspect the wiring harness for physical cable problems, such as chafing, shorts to ground, or open circuits that could corrupt the CAN signal

3. 3

   Check the Driveline Retarder controller for internal defects or software glitches that would cause it to get stuck broadcasting a continuous negative torque demand

4. 4

   Use the CNH EASy diagnostic tool to check for related CAN bus timeout errors (e.g., Timeout Error of CAN-Receive-Frame RCDR from retarder)

1. 1

   Confirm fault code

   Connect the CNH diagnostic tool to confirm that DTC 3946 (7CE) is active or logged.

2. 2

   Test CAN bus wiring

   Visually and electrically test the CAN bus wiring harness connecting the Driveline Retarder to the Engine ECM.

3. 3

   Repair wiring and connectors

   Repair any damaged wires, clean corroded pins, and ensure all connectors are securely seated.

4. 4

   Replace Driveline Retarder controller

   If the wiring is fully intact and the CAN bus is operating normally, the fault lies within the Driveline Retarder controller itself (broadcasting an erroneous continuous signal). Replace the defective Driveline Retarder controller.

5. 5

   Clear codes and test

   Clear the fault codes from the EDC and test-run the machine to verify the retarder operates correctly without triggering the code.