What is Sany SY485H Fault Code E105?

Fault Code E105 on the Sany SY485H excavator indicates a communication error or malfunction with the Engine Control Module (ECM) and the machine's main controller system. This diagnostic trouble code (DTC) specifically relates to a CAN bus communication failure between the engine ECM and the display/monitoring system, preventing proper data exchange between critical control units.

The CAN (Controller Area Network) bus is the digital communication backbone that allows the engine controller, hydraulic controller, and display panel to share real-time operational data. When E105 triggers, the ECM cannot properly communicate engine parameters such as RPM, temperature, fuel consumption, or diagnostic information to the operator display. This is particularly critical on the SY485H because the integrated control system relies on continuous ECM feedback to optimize hydraulic flow, manage fuel efficiency, and protect the engine from damage. Without proper communication, the machine may enter a derate mode or fail to start altogether, significantly impacting productivity and potentially masking other developing issues.

Common Symptoms

• Warning light illuminated on the instrument cluster with E105 displayed on the monitor screen
• Intermittent or complete loss of engine data on the display (no RPM reading, fuel level, or temperature gauges)
• Engine derate mode activated, limiting maximum RPM or hydraulic performance
• Machine fails to start or starts but immediately shuts down due to communication timeout
• Erratic gauge behavior with needles jumping or freezing during operation

Potential Causes

The E105 code on used SY485H excavators typically stems from several age-related and environmental factors:

• Corroded or loose CAN bus connectors at the ECM, particularly the 24-pin main harness connector which is exposed to engine bay heat and vibration
• Damaged wiring harness with breaks or shorts in the twisted-pair CAN communication wires, especially at rub points near the engine mount or along the chassis rail
• Failed terminating resistor (120-ohm) at either end of the CAN bus network
• ECM internal failure or corrupted firmware, more common in machines with over 6,000 operating hours
• Voltage supply issues to the ECM due to faulty main relay, poor ground connections, or battery voltage fluctuations
• Water intrusion into ECM housing or connector seals, common on machines operated in wet conditions

How to Troubleshoot and Fix Code E105

Step 1: Visual Inspection and Connector Check Begin by inspecting all wiring harnesses between the ECM (located behind the right-side service panel) and the main controller. Check for obvious damage, chafing, or connector corrosion. On used excavators, pay special attention to harness routing near moving components and heat sources. Disconnect and reconnect the ECM connector, examining pins for corrosion, bent terminals, or moisture. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: CAN Bus Voltage and Resistance Testing Using a digital multimeter, measure the voltage on the CAN-High and CAN-Low wires at the ECM connector with the key in the ON position (engine off). You should see approximately 2.5V on each line with a 0V differential when idle. Next, turn the key OFF and measure resistance between CAN-High and CAN-Low terminals—you should read approximately 60 ohms (indicating two 120-ohm terminating resistors in parallel). A reading of 120 ohms suggests one terminating resistor has failed; an open circuit indicates wiring breaks or both resistors failed.

Step 3: ECM Power Supply and Ground Verification Verify the ECM receives proper battery voltage (24V nominal on SY485H) at the power supply pins with the key ON. Check for voltage drop across ground connections—less than 0.1V drop is acceptable. Inspect the main relay supplying ECM power, as intermittent relay failure is common on machines beyond 5,000 hours. If voltage and grounds are correct, use Sany PC-E diagnostic software to attempt ECM communication and check for firmware corruption or internal ECM faults.

Step 4: Replacement and Verification If diagnostics point to ECM failure after confirming wiring integrity, replacement may be necessary. For used excavators, always verify replacement ECM compatibility with your specific engine serial number. After repairs, clear fault codes using diagnostic software and perform a CAN bus health check to confirm communication stability under various RPM conditions before returning to service.

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Disclaimer: This guide provides general troubleshooting information for Sany SY485H excavators. Always consult the official Sany service manual for your specific machine serial number and consider professional diagnostic support for complex electrical issues. Improper repairs to CAN bus systems can cause additional control module damage.