What is Komatsu PC110-8M0 Fault Code CA144?

Fault Code CA144 on the Komatsu PC110-8M0 indicates a malfunction in the Engine Control Module (ECM) communication circuit, specifically related to the CAN (Controller Area Network) data link between the engine controller and the machine's main monitor system. This diagnostic trouble code triggers when the ECM detects an interruption, degradation, or complete loss of communication signals on the CAN bus network that coordinates engine performance with hydraulic systems and operator displays.

This code is critical for the PC110-8M0 because this mid-sized excavator relies on integrated electronic communication between the engine ECM and the machine controller to optimize fuel efficiency, manage hydraulic flow, and provide real-time diagnostic information to the operator. When communication fails, the machine cannot properly coordinate engine output with work demand, potentially causing performance issues or entering a protective derate mode.

Common Symptoms

• Warning light illumination on the dashboard, typically the engine malfunction indicator or service lamp
• Intermittent or complete loss of engine parameter display on the monitor (RPM, coolant temperature, fuel level may disappear or freeze)
• Reduced engine power or unexpected derate to lower RPM ranges as a protective measure
• Hydraulic system responsiveness issues, including sluggish boom or bucket movements due to improper load-sensing coordination
• Diagnostic monitor errors or inability to access machine information through the cab display panel

Potential Causes

On used Komatsu PC110-8M0 excavators, CA144 typically results from:

• Damaged or corroded CAN bus wiring harness, especially at known wear points near the engine firewall, behind the battery box, or along the right-hand chassis rail where harnesses experience vibration and environmental exposure
• Loose or oxidized connector terminals at the ECM (mounted near the fuel filter assembly) or at the main machine controller connector
• Failed termination resistors within the CAN network—these 120-ohm resistors can degrade over time in high-vibration environments
• ECM internal communication circuit failure, more common in machines with over 6,000 operating hours or those exposed to water intrusion events
• Voltage supply issues to either controller, including poor grounds at the engine block grounding strap or corroded battery terminals affecting system voltage stability

How to Troubleshoot and Fix Code CA144

Step 1: Visual Inspection Begin with a thorough physical inspection of the CAN bus harness routing from the engine ECM to the machine controller. On used excavators, check for harness chafing against the engine block, fuel lines, or structural components. Inspect all connectors for corrosion, bent pins, or moisture intrusion—the main ECM connector and the 20-pin machine controller connector are particularly vulnerable on older units.

Step 2: Electrical Testing Using a digital multimeter, verify the CAN-High and CAN-Low signal wires for proper continuity and resistance. With the ignition off and connectors unplugged, measure resistance between CAN-H and CAN-L terminals—you should read approximately 60 ohms (two 120-ohm termination resistors in parallel). If you measure infinite resistance, a termination resistor has failed or a wire is open. Check for shorts to ground on both CAN lines (should read infinite resistance to chassis ground).

Step 3: Voltage and Signal Verification With ignition on but engine not running, use a multimeter or oscilloscope to check for voltage presence on the CAN bus—you should see approximately 2.5V on both CAN-H and CAN-L when idle, with differential voltage changes during communication. If no voltage is present, verify the 5V reference supply from the ECM to the network. For used machinery, poor grounding is extremely common—verify less than 0.5 ohms resistance between ECM ground terminal and battery negative.

Step 4: Component Testing If wiring checks pass, suspect controller issues. If available, use Komatsu KOMTRAX diagnostic software or compatible scan tools to monitor live CAN bus traffic and identify which controller is failing to communicate. Swap suspect components with known-good units if possible, or consult with a Komatsu dealer regarding ECM reflashing or replacement—on used machines, ECM moisture damage from compromised engine compartment seals is a frequent culprit.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number, and consider professional diagnostic assistance for complex electrical issues. Improper troubleshooting can cause additional damage to electronic systems.