How to fix CAN bus communication errors on your excavator

Your excavator's display goes blank. The joystick feels dead. A generic "communication error" flashes on the screen. You're losing billable hours, and you don't know if it's a bad ECU, a broken wire, or something else entirely.

CAN bus communication errors are among the most frustrating problems on modern excavators. But here's the truth: most of these faults are not caused by failed electronic modules. They're caused by wiring issues, bad connections, or termination problems. Replacing expensive ECUs or joysticks without proper diagnostics is a costly mistake.

This guide walks you through a proven troubleshooting sequence. Follow it step by step, and you'll isolate the root cause fast.

What is a CAN bus error?

The Controller Area Network (CAN) bus is the nervous system of your excavator. It allows the engine ECU, joystick controllers, display, and other modules to talk to each other. When communication breaks down, the machine may enter derate mode, lose joystick response, or refuse to start.

Common fault codes include U2106 (CAN communication timeout) and U0073 (CAN bus off). These codes tell you there's a network problem, but they don't tell you where. That's where systematic troubleshooting comes in.

Step 1: Check the basics first

Before you dive into wiring diagrams, do these three checks:

• Verify power and ground. A module with low voltage can corrupt CAN traffic. Check battery voltage at the diagnostic connector. It should be above 12.5V on a 12V system.
• Inspect fuses. A blown fuse to a CAN node can take down the entire bus. Check all fuses related to the electronic control system.
• Look for obvious damage. Open the harness covers and look for rubbed wires, corrosion, or melted insulation. A single shorted wire can silence the whole network.

Step 2: Measure termination resistance

A properly terminated CAN bus should read 60 ohms between CAN High and CAN Low at the diagnostic port. This is because two 120-ohm resistors are wired in parallel at each end of the bus.

• If you read 120 ohms, one termination resistor is missing or open.
• If you read 0 ohms, there's a short between the CAN wires.
• If you read infinite resistance, the bus is open.

Use a digital multimeter set to resistance mode. Disconnect the battery before measuring.

Step 3: Check for shorts to ground or power

The resistance between each CAN wire and chassis ground should be very high (megaohms). A low reading means a short to ground. Similarly, check for shorts to battery positive.

This step catches the most common fault: a rubbed wire touching the machine frame.

Step 4: Isolate the faulty node

If the bus wiring checks out, the problem is likely a defective module. Here's how to find it:

1. Disconnect all CAN nodes except the diagnostic tool.
2. Reconnect modules one at a time while monitoring the bus.
3. When the error returns, you've found the culprit.

This method works because a failed module can pull the entire bus down. A known example: a shorted joystick controller can cause a "CAN bus off" condition that affects every other module.

Step 5: Inspect connectors and backshells

Corrosion in connectors is a leading cause of intermittent CAN faults. Pull each connector, inspect for green or white corrosion, and clean with electrical contact cleaner. Apply dielectric grease before reconnecting.

Pay special attention to connectors near the cab floor, under the hood, and around the radiator. These areas collect moisture and debris.

When to call in a specialist

If you've completed all five steps and the fault persists, the issue may be inside a sealed module. Internal CAN transceiver failures are rare but do happen. At this point, you need a repair partner with diagnostic tools that can communicate directly with the module's microcontroller.

How the Resident Expert Can Help

RE-CLICK specializes in diagnosing and repairing the exact electronic components that cause CAN bus failures on excavators. Their certified technicians use proprietary test systems to isolate faults inside ECUs, joysticks, and sensor modules. Instead of replacing expensive parts, they repair the root cause and return your module ready to install. Nationwide support means you can ship your component and get it back fast, reducing downtime to days instead of weeks.