Case IH F-1235-31 - ECU – Engine Control Unit (ECU): CAN Bus: Error passive CAN Bus Node / CAN communication for erroneous behaviour of a participant

The CAN controller is receiving or sending erroneous messages, forcing the node to go "passive" or offline to protect the rest of the network. It frequently indicates a physical wiring issue, a missing/failed termination resistor, or a power/ground fault originating from the ATS (Aftertreatment System) relay, which prevents the CAN network from transmitting messages.

• MAGNUM AFS Connect
• Case IH Steiger and Quadtrac series
• Case IH Magnum and Puma series
• Case IH Austoft 9900 sugarcane harvesters
• Various Case IH combines and sprayers

1. 1

   Check the CAN termination resistors for proper network resistance (should measure approximately 60 ohms across CAN High and CAN Low)

2. 2

   Inspect network connections and contacts for moisture, corrosion, or loose pins

3. 3

   Check for short circuits to an external power source, ground, or between CAN High and CAN Low

4. 4

   Check for power, continuity, and short circuit conditions at the ATS (Aftertreatment System) relay and its associated wiring

1. 1

   Power Down

   Turn off the key and disconnect the battery to prevent electrical spikes.

2. 2

   Locate the CAN C Bus

   Locate the diagnostic connector or the specific CAN C / CAN 3 bus wiring harness near the Engine ECU.

3. 3

   Measure Resistance

   Using a multimeter, measure the resistance between the CAN High and CAN Low pins. If it reads ~60 ohms, the termination resistors are intact. If it reads ~120 ohms, one terminating resistor is missing, failed, or there is an open circuit in the harness. If it reads <10 ohms or 0 ohms, there is a short circuit.

4. 4

   Wiggle Test

   Wiggle the harness during measurement (especially near the ATS relay and ECU connectors) to reveal any intermittent chafing or internal wire breaks.

5. 5

   Repair Wiring/Resistors

   Repair any damaged wiring or replace faulty 120-ohm termination resistors.

6. 6

   Software/ECU Check

   If the measured resistances are correct (60 ohms) and neither conductor is grounded, check the ECU for the appropriate software and re-flash if necessary.

7. 7

   ECU Replacement

   If the error persists after verifying wiring, relays, and software, the ECU's internal CAN controller is likely defective, and the ECU must be replaced.