What is Doosan DX500LC-9C Fault Code E000656-09?

Fault Code E000656-09 indicates a communication error or voltage abnormality in the main control system's CAN (Controller Area Network) bus, specifically related to the machine's integrated control module network. This diagnostic trouble code (DTC) typically signals that the Electronic Control Unit (ECU) has detected an intermittent or complete loss of communication between critical control modules, or an out-of-range voltage condition on the CAN bus circuit.

In the Doosan DX500LC-9C excavator, the CAN bus serves as the central nervous system, allowing the engine controller, hydraulic controller, and monitor display to communicate seamlessly. When this code triggers, it compromises the machine's ability to coordinate hydraulic functions with engine performance, potentially leading to operational inefficiencies or complete system shutdowns. For used excavators, this fault often stems from aging wiring harnesses or corroded connections rather than controller failures.

Common Symptoms

• Intermittent or complete loss of monitor display functionality, with the screen going blank or showing error messages
• Erratic hydraulic performance, including unexpected boom/arm movements or reduced swing speed due to controller miscommunication
• Engine derate mode activation, where the machine limits power output as a protective measure
• Multiple warning lights illuminating simultaneously on the instrument cluster, including the master caution light
• Inability to access diagnostic information through the standard operator interface

Potential Causes

The E000656-09 code in used DX500LC-9C excavators typically results from these technical failures:

• Damaged or corroded CAN bus wiring harness, particularly at known rub points near the swing bearing and along the upper structure where cables flex during operation
• Loose or oxidized connector pins at the main ECU or hydraulic controller connection points, common in machines with 5,000+ operating hours
• Voltage supply issues from the machine's electrical system, including failing alternators or poor ground connections at the battery box
• Water intrusion into sealed connectors, especially in excavators operated in wet conditions without proper harness protection
• Failed termination resistors on the CAN bus network (120-ohm resistors at network endpoints)
• ECU internal faults due to voltage spikes or age-related component degradation

How to Troubleshoot and Fix Code E000656-09

Step 1: Visual Harness Inspection Begin by thoroughly inspecting all CAN bus wiring from the main controller harness to each control module. Focus on areas where cables pass through the swing bearing and near hydraulic valve banks. Look for abraded insulation, pinched wires, or evidence of previous repairs. On used machines, check for aftermarket modifications that may have compromised wire routing.

Step 2: Connector and Voltage Testing Disconnect the main ECU connector and inspect pins for corrosion, bent contacts, or moisture. Using a digital multimeter, verify battery voltage (12-14V) at the power supply pins with the key on. Test CAN-High and CAN-Low circuit resistance—you should read approximately 60 ohms between these two wires with all modules connected, indicating proper termination resistors.

Step 3: Communication Circuit Diagnosis With a Doosan DX diagnostic software (G-SCAN or equivalent), monitor real-time CAN bus activity. Check for communication dropouts or error frame counts. If voltage readings are correct but communication fails, test each termination resistor (located at network endpoints) by disconnecting modules sequentially and measuring resistance. Replace any resistor not reading 120 ohms. For persistent issues on used excavators, inspect the swing bearing slip ring assembly for worn contacts that can interrupt CAN signals.

Step 4: Controller and Ground Verification Verify all ground connections at the battery, frame rails, and controller mounting points show less than 0.5 ohms resistance to chassis ground. If all wiring checks pass, the fault may indicate an internal ECU failure—consider swapping controllers with a known-good unit before purchasing replacements, as used excavator ECUs can often be reprogrammed and tested.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Doosan service manual for your specific serial number, and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional system damage or safety hazards.