Case IH 3943 – Engine Control Unit (ECU) / Electronic Diesel Control (EDC): Torque or speed control demand from Transmission Controller Retarder exceeding the maximum time

This is a CAN bus communication and logic error. It indicates that the transmission retarder is sending a continuous demand signal for torque or speed control to the engine that has exceeded the maximum allowable time limit programmed into the system. This usually points to a stuck retarder switch, a short in the retarder control circuit, or a CAN bus communication glitch preventing the "off" signal from being processed.

• Magnum
• Steiger
• MX series
• combines
• 330B

1. 1

   Battery and Voltage Check: Verify battery voltage is between 12V and 14V, and check the alternator output.

2. 2

   CAN Bus Communication Test: Check for other CAN bus timeout codes (e.g., lost communication with the Transmission Controller). Inspect the yellow and green CAN bus wires for continuity, shorts, or corrosion.

3. 3

   Terminating Resistor Check: Measure the resistance across the CAN High and CAN Low pins at the diagnostic connector; it should read approximately 60 ohms.

4. 4

   Retarder Switch/Sensor Inspection: Monitor the transmission controller voltage and retarder demand signals using a dealer service tool or the in-cab Pro 700 display. Check the physical retarder controls (switches/levers) to ensure they are not mechanically stuck in the engaged position.

5. 5

   Wiring Harness Inspection: Check the wiring harness between the transmission retarder, the TCM, and the ECU for chafed wires or a short to power/ground that would cause a continuous demand signal.

1. 1

   Disconnect Power

   Disconnect the negative battery cable before performing any electrical repairs to prevent shorting out sensitive modules.

2. 2

   Clean Connections

   Clean the battery cables and the CAN bus diagnostic connectors, which are often located under the right-hand console or steering column.

3. 3

   Repair Wiring

   If the diagnostic checks revealed chafed wires or corroded pins in the harness connecting the retarder to the TCM, splice in new wiring or replace the damaged connector pins.

4. 4

   Replace Faulty Controls

   If the retarder switch or sensor is mechanically stuck or internally shorted (causing the continuous demand), remove the trim panels accessing the switch and replace the unit.

5. 5

   Replace CAN Terminator

   If the CAN bus resistance is out of spec, locate and replace the faulty CAN bus terminating resistor.

6. 6

   TCM Replacement (Worst Case)

   If the wiring and sensors are perfectly intact but the Transmission Controller is internally shorted and failing to drop the demand signal, the TCM must be replaced. Note: A new TCM will require dealer programming to sync with the tractor's ECU.

7. 7

   Clear Codes and Test

   Reconnect the battery, clear the fault codes using a diagnostic tool, and test operate the machine. Engage and disengage the retarder to verify it operates within normal time limits without throwing the code.