Case IH 3945 – Engine Control Unit (ECU) / EDC (Electronic Diesel Control): Torque or speed control demand from ABS/ESR/ESP Retarder exceeding the maximum time.

A CAN Bus communication and logic error where the engine management system receives a continuous, prolonged request over the CAN bus from the Anti-lock Braking System (ABS), Electronic Slip Reduction (ESR), or Electronic Stability Program (ESP) retarder to limit engine torque or speed. This torque-reduction demand has exceeded the maximum allowable programmed time limit.

• Steiger
• Magnum
• Puma
• Optum
• Axial-Flow

1. 1

   Scan for associated codes using the CNH Electronic Service Tool (EST) to check for other CAN bus timeout errors or specific faults logged directly inside the ABS/ESP control module.

2. 2

   Monitor live CAN bus data for the retarder torque demand signals to check if the ABS/ESP module is actively commanding a torque reduction while the machine is operating normally and the retarder is physically disengaged.

3. 3

   Verify that the physical retarder control switch, lever, or pedal is not mechanically stuck, shorted to ground, or sending a continuous active signal to the module.

4. 4

   Inspect the CAN bus wiring harness and connectors between the ABS/ESR/ESP control module, the retarder, and the Engine ECU for chafing, corrosion, or loose pins that could cause data frame errors.

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 the Retarder Controls

   Locate the retarder control switch/sensor in the cab. Test it with a multimeter for continuity. If the switch is internally shorted and sending a continuous 'ON' signal, remove and replace the switch.

3. 3

   Harness Repair

   Inspect the wiring harness connecting the ABS/ESP module to the Engine ECU. Repair any broken wires or clean corroded connector pins. Ensure the CAN High and CAN Low lines have the proper resistance (typically 60 ohms across the circuit).

4. 4

   Module Replacement (if necessary)

   If the wiring and switches are intact but the ABS/ESP control module is still broadcasting erroneous continuous torque-limit CAN messages, the module itself is likely suffering from an internal logic failure. Replace the ABS/ESP module.

5. 5

   Clear and Test

   Reconnect the battery. Connect the CNH diagnostic tool, clear fault code 3945, and perform a test drive to verify the retarder operates correctly and the code does not return.