Case IH 5122-19 - UCM – UCM: Loss of communication between the vehicle controller and the PCM

A fault is declared when no valid message is received from the auto-guidance controller (PCM) within the 250 ms Active Message Timeout window, specifically while the Steering Mode Current State signal changes from GPS1 steering to any off-road state.

• MAGNUM AFS Connect
• Steiger AFS Connect
• Steiger 470 AFS Connect
• Magnum
• Optum
• Puma
• Patriot sprayers
• Axial-Flow combines

1. 1

   Verify that the UCM/VCM and the PCM modules are receiving the correct power supply voltage.

2. 2

   Turn the ignition key to the ON position and check the CAN bus connections and pin readings at the PCM connector X-086. Measure Pin F4 (CAN2 Low) to chassis ground (expected 2.2 - 2.5 V) and Pin E4 (CAN2 High) to chassis ground (expected 2.5 - 2.8 V).

1. 1

   Resolve Power Issues

   If the power supply to the modules is incorrect, trace the power circuits, check fuses/relays, and repair the power supply issue. If power is OK, proceed to step 2.

2. 2

   Repair CAN Bus Wiring

   If the pin readings at connector X-086 are out of specification, there is a physical wiring issue. Locate and repair the failed CAN bus connections, broken wires, or shorts in the harness. If readings are correct, proceed to step 3.

3. 3

   Software Update

   If the wiring and power supply are intact, the issue is likely software-related. Download the most current software version for the UCM and PCM using the Electronic Service Tool (EST) and reconfigure the components.

4. 4

   System Test

   Clear the fault codes and test the remote system operation. If the fault code does not return, return the tractor to normal operation. If the code returns, the official manual advises escalating the concern to the Technical Help Desk (THD), which typically precedes replacing the faulty UCM or PCM hardware.