Case IH INST12043 – ICU: Communications Lost with Data Bus 1 and ALL other controllers.

The Instrument Cluster Unit (ICU) has detected a critical failure in the tractor's Controller Area Network (CAN) communication system, specifically a complete loss of communication on Data Bus 1. This indicates that the ICU is not receiving data from any of the other electronic control units (ECUs) on that network, which can lead to the shutdown of certain machine functions as a safety precaution.

• Magnum 235-340
• MX Magnum
• Magnum 7110
• Magnum 7120
• Magnum 7130
• Magnum 7140
• Magnum 7150
• Magnum 7210
• Magnum 7220
• Magnum 7230
• Magnum 7240
• Magnum 7250
• Magnum 8910
• Magnum 8920
• Magnum 8930
• Magnum 8940
• Magnum 8950

1. 1

   Visually inspect the wiring harnesses associated with Data Bus 1 for physical damage, cuts, abrasions, moisture intrusion, or corrosion at connector points.

2. 2

   Perform a CAN Bus Resistance Check with the ignition off and battery disconnected. Measure resistance between CAN High and CAN Low pins (should be approximately 60 Ohms).

3. 3

   Perform Voltage Checks with the ignition on and engine off. Measure DC voltage between CAN High to ground (should be 2.5V - 2.7V) and CAN Low to ground (should be 2.3V - 2.5V).

4. 4

   Check for Shorts to Ground with power off. Measure resistance from the CAN High and CAN Low pins to ground (should read very high/open circuit).

1. 1

   Confirm the Fault

   Start the tractor and verify that the INST12043 fault code is active.

2. 2

   Perform Resistance Test

   Conduct the CAN bus resistance check to determine the state of the network wiring and terminating resistors.

3. 3

   Address Incorrect Resistance Readings

   If 120 Ohms: Locate the two terminating resistors (often one in the ECM and one in the harness), inspect their wiring and connections, and replace any missing or faulty resistor. If 0 Ohms: Inspect the wiring harness for a short circuit between CAN High and CAN Low. If Open Circuit: Visually inspect the harness and check continuity from one end to the other to pinpoint the break.

4. 4

   Isolate the Faulty Component

   If wiring and resistance are correct, use a 'half-split' method. Disconnect a module in the middle of the network and re-measure resistance. If normal, the fault is in the disconnected module or its harness section. If it persists, the issue is in the other half of the network. Continue this process of disconnecting modules to isolate the source of the problem.

5. 5

   Check the Instrument Cluster

   Inspect the electrical connector at the back of the cluster for corrosion or loose pins. If all other components and wiring check out, the Instrument Cluster Unit itself may be faulty.

6. 6

   Clear Codes and Verify Repair

   After replacing a faulty component or repairing wiring, clear the fault codes using a diagnostic tool and operate the tractor to ensure the code does not return.