Case IH 426 – Engine Control Module (ECM): SAE J1939 Data Link - Cannot Transmit

Communication between the Engine Control Module (ECM) and another device on the SAE J1939 data link has been lost. Specifically, the fault occurs when the ECM successfully starts communicating with another device on the J1939 CAN bus, but then suddenly can no longer transmit data.

• MX Magnum
• STX Steiger
• Case IH Steiger and Quadtrac series
• Case IH Magnum series
• Case IH Patriot/SPX Sprayers
• Any Case IH machine equipped with 8.3L, 9L, or 15L electronically controlled engines.

1. 1

   Check for ECM Communication: Connect an INLINE data link adapter to the vehicle's 9-pin SAE J1939 diagnostic connector. Turn the keyswitch ON and attempt to communicate with the ECM using the INSITE electronic service tool (or equivalent Case IH EST).

2. 2

   Inspect the Harness and Connectors: Disconnect the ECM and inspect the OEM harness and ECM connector pins. Look for dirt, debris, moisture, missing seals, corroded pins, bent/broken pins, or pushed-back/expanded pins.

3. 3

   Bench Test the ECM: If the ECM will not communicate on the machine, remove it and connect it to an ECM bench calibration harness. If the service tool communicates with the ECM on the bench, the vehicle's J1939 harness is faulty. If it still does not communicate, the ECM itself has failed.

1. 1

   Key Off

   Turn the keyswitch OFF and disconnect the battery ground to prevent electrical spikes.

2. 2

   Clean and Repair Connectors

   If the diagnostic inspection revealed moisture or debris in the ECM connectors, clean the pins thoroughly with electrical contact cleaner. If pins are bent or pushed back, carefully realign them or replace the damaged terminal ends.

3. 3

   Check Bus Resistance

   With the batteries disconnected, measure the resistance across the J1939 CAN High and CAN Low pins at the diagnostic connector. A healthy J1939 bus should read exactly 60 ohms (indicating two 120-ohm terminating resistors are present and the wiring is intact). If it reads 120 ohms, one resistor or a segment of the harness is broken. If it reads 0 ohms, the bus is shorted.

4. 4

   Isolate the Faulty Module

   If the bus is flooded or shorted, unplug modules on the J1939 network (e.g., transmission TCU, instrument cluster, armrest controller) one by one. Check if ECM communication restores after a specific module is unplugged. Replace the module that is tying up the data link.

5. 5

   Validate the Repair

   Reconnect all components and turn the keyswitch ON. Connect the electronic service tool. Start the engine and let it idle for 1 minute.

6. 6

   Clear Codes

   Verify that Fault Code 426 has changed to an INACTIVE status. Use the "Reset All Faults" command in the service tool to clear the inactive codes from the ECM memory.