Case IH 518020-19 - DEC – DEC: CAN VB2 VCM heart beat message received network data in error

Communication failure on the CAN bus network. The module logging the fault is not receiving the expected periodic "heartbeat" signal from the Vehicle Control Module (VCM) over the Vehicle Bus 2 (CAN VB2) network, or the data update rate is abnormal.

• MAGNUM AFS Connect
• Case IH Magnum AFS Connect Series (e.g., Magnum 280, 310, 340, 380, 400)
• Case IH Steiger & Quadtrac AFS Connect Series

1. 1

   Connect the Case IH Electronic Service Tool (EST) to the diagnostic connector (CAN1/ISOBUS) to confirm if the fault is currently active or stored historically

2. 2

   Verify that the VCM (Vehicle Control Module) is receiving proper unswitched power, switched power, and ground. A module that is powering down intermittently will drop its heartbeat message.

3. 3

   Inspect the connectors at both the DEC and the VCM for moisture, corrosion, backed-out pins, or damage

4. 4

   Measure the resistance across the CAN High and CAN Low pins for the VB2 network. A healthy CAN bus should read approximately 60 ohms (indicating two 120-ohm terminating resistors in parallel).

5. 5

   If the reading is 120 ohms, one terminating resistor is missing or there is an open circuit in the wiring.

6. 6

   Check for shorts to ground or shorts to power on the CAN High and CAN Low wires between the DEC and VCM

1. 1

   Disconnect Battery

   Always disconnect the main battery power before servicing sensitive CAN bus wiring or modules.

2. 2

   Repair Wiring/Connectors

   If the diagnostic checks reveal an open circuit, short, or damaged connector on the CAN VB2 network, repair the wiring harness or replace the damaged connector pins.

3. 3

   Replace Terminating Resistor

   If the CAN bus resistance check failed due to a faulty passive terminator, locate and replace the terminating resistor on the VB2 network.

4. 4

   Replace Faulty Module

   If the wiring, power, ground, and terminating resistors all test perfectly, the fault lies internally within either the VCM (failing to broadcast) or the DEC (failing to receive). Replace the faulty module.

5. 5

   Reprogramming

   If a module (DEC or VCM) is replaced, connect the EST to the diagnostic port. Navigate to the configuration menu and flash the correct software and configuration settings for the specific tractor model and transmission type.

6. 6

   Clear Codes and Test

   Clear the fault codes using the EST, cycle the key, and operate the tractor to ensure the 518020-19 code does not return.