Case IH 3541 – Engine Control Unit (ENG / EDC) / EDC7UC31: CAN Message timeout SCR1 (from DCU) - CAN timeout

Loss of Controller Area Network (CAN) communication between the engine management system and the Selective Catalytic Reduction (SCR) system. The Engine Control Unit expects to receive a regular data packet known as the 'SCR1' message from the Dosing Control Unit (DCU). When this message is not received within the programmed time limit, the system logs a CAN timeout.

• Case IH Magnum 235 - 340 (Series 4)
• Case IH Puma series (165, 185, 215, 230)
• Case IH Maxxum EP Efficient Power series (110, 125)
• Case IH Farmlift Telehandlers (632, 635, 735, 742, 935)

1. 1

   Calibration Check: Verify the calibration status of the Engine ECU and the DCU using the CNH Electronic Service Tool (EST). Ensure all software is up to date, as fault monitor updates are sometimes released to resolve false DSI/DCU faults.

2. 2

   Diagnostic Scan: Use the diagnostic tool to ping the DCU directly. Check if the DCU is broadcasting its own internal errors (such as EEPROM failures or internal voltage faults) which would indicate a dead module.

3. 3

   Wiring and Harness Inspection: Inspect the CAN bus wiring harness running from the Engine ECU to the SCR DCU for chafing, cuts, or corrosion.

4. 4

   Power and Ground Check: Load test the power and ground circuits supplying the DCU. If the DCU loses power, it will drop off the CAN bus and trigger this timeout.

5. 5

   Connector Pin Drag Test: Disconnect the harnesses at the DCU and perform a pin drag test to verify that the connector pins are making proper, secure contact and have not been pushed back or broken.

1. 1

   Check and update calibrations

   If the diagnostic tool reveals that the module calibrations are outdated, flash the Engine ECU and DCU with the latest software using the CNH EST tool, then retest.

2. 2

   Repair or replace connectors

   If the pin drag test fails or connectors are cracked, replace the damaged connector bodies or repin the harness to ensure a secure connection.

3. 3

   Repair wiring harness

   If wiring damage (chafing/corrosion) is found on the CAN lines or power/ground circuits, repair the wiring harness, route it safely away from abrasion points, and retest.

4. 4

   Replace SCR Dosing Control Unit

   If the wiring, power, ground, and CAN bus integrity are all confirmed to be good, but the DCU still fails to communicate (or has internal EEPROM failure codes), the SCR Dosing Control Unit / Dosing Module has failed and must be replaced.

5. 5

   Install and program new DCU

   Install the new DCU, connect the DEF lines and electrical harnesses, and use the CNH EST to program/configure the new module to the tractor.

6. 6

   Clear codes and verify repair

   Clear all inactive fault codes and run the engine to verify that the SCR1 CAN message is restored and the fault does not return.