Case IH 520331-14 - BCM – BCM: CAN Bus C - curto entre as linhas CAN_L e CAN_H (CAN Bus C - short circuit between the CAN_L and CAN_H lines)

Critical communication failure on the machine's network caused by a short circuit between the CAN_L and CAN_H lines on CAN Bus C, preventing any signals from being transmitted across that network segment.

• MAGNUM AFS Connect
• Magnum AFS Connect 180
• Magnum AFS Connect 200
• Magnum AFS Connect 220
• Magnum AFS Connect 240
• Magnum AFS Connect 250
• Magnum AFS Connect 280
• Magnum AFS Connect 310
• Magnum AFS Connect 340
• Magnum AFS Connect 380
• Magnum AFS Connect 400
• Steiger

1. 1

   Perform a resistance test across the CAN_H and CAN_L pins with the machine powered off (expected reading is approximately 60 ohms for a healthy 2-terminator bus)

2. 2

   Verify the short circuit by disconnecting the battery and measuring resistance between CAN_L and CAN_H on Bus C; a reading near 0 ohms confirms the short

3. 3

   Isolate the cause by disconnecting modules on CAN Bus C one at a time (including the BCM) to see if resistance returns to normal, which would indicate an internal module short

4. 4

   Inspect the wiring harness for damage, chafing, or pinch points under the cab or near moving parts if the short persists after unplugging all modules and terminators

1. 1

   Disconnect battery

   Turn off the ignition key and disconnect the tractor's battery to prevent electrical damage during testing.

2. 2

   Locate connector

   Locate a diagnostic port or an accessible module connector for CAN Bus C.

3. 3

   Probe pins

   Using a digital multimeter, probe the CAN_H and CAN_L pins to confirm the short circuit (near 0 ohms).

4. 4

   Isolate network

   Begin isolating the network by unplugging the BCM and other modules on CAN Bus C one by one. Monitor your multimeter.

5. 5

   Replace module

   If unplugging a specific module clears the short, replace that module.

6. 6

   Trace wiring harness

   If the short persists with all modules disconnected, trace the CAN Bus C wiring harness. Look for pinch points, melted insulation, or chafing against the tractor chassis.

7. 7

   Repair or replace wiring

   Repair the damaged twisted-pair wiring using standard CAN bus repair procedures (maintaining the twist as close to the repair as possible), or replace the affected harness section.

8. 8

   Replace terminating resistor

   If a terminating resistor is found to be melted or internally shorted, replace it.

9. 9

   Reconnect components

   Reconnect all modules and the battery.

10. 10

    Clear fault codes

    Connect a diagnostic service tool (such as the Case IH EST or Jaltest) to clear the inactive fault codes and verify that CAN Bus C communication has been restored.