Case IH tCB – PCU: CAN In PCU, Shorted To High Source

The system has detected that the Controller Area Network (CAN) communication line at the Pump Control Unit (PCU) is short-circuited to a high voltage source (typically 12 volts).

• MXM
• MXM 120
• MXM 130
• MXM 140
• MXM 155
• MXM 175
• MXM 190

1. 1

   Check for other error codes: If any other error codes are displayed, diagnose and resolve those first.

2. 2

   Verify Power Supply: Check that the tractor battery power supply has not been improperly connected to an external power supply (e.g., incorrect jump-starting).

3. 3

   Visual Inspection: Inspect the wiring harness and connectors for damage, corrosion, or loose pins. Ensure all connections are tight.

4. 4

   Prepare for Testing: Turn the power and keyswitch OFF. Disconnect the connectors at both ends of the circuit to prevent false readings during resistance testing.

1. 1

   Test the Engine Control Module (ECM) Circuit

   Disconnect the engine control module connector C315. Measure the resistance between connector C277 pin 3 (Y) and C315 pin 12 (5400–Y). Measure the resistance between connector C277 pin 4 (G) and C315 pin 11 (5420–G). Wiggle the harness and the connectors while testing to check for an intermittent circuit. If the resistance indicated is greater than approximately 5 Ohms, repair or replace the wiring harness. If the harness tests okay, the Engine Control Module may need to be replaced.

2. 2

   Test the Central Controller (XCM) Circuit

   Measure the resistance between connector C277 pin 3 (Y) and C324 pin 15 (5400–Y). Measure the resistance between connector C277 pin 4 (G) and C324 pin 16 (5420–G). Wiggle the harness and connectors. If the resistance is greater than 5 Ohms, repair or replace the harness. If the harness is okay, remove and replace the Central Controller (XCM).

3. 3

   Check Software Levels

   Download/flash the correct level of software into the Central Controller (XCM) and the Engine Control Module. If the fault re-occurs after a software update and harness verification, replace the Central Controller (XCM).

4. 4

   Finalize

   Once the root cause is rectified, clear the error code and test the system for normal operation.