Doosan DX150LC-9C Fault Code E520708-12: Complete Diagnostic Guide

What is Doosan DX150LC-9C Fault Code E520708-12?

Fault Code E520708-12 indicates a communication error or voltage abnormality in the Engine Control Module (ECM) to Hydraulic Main Control Valve (MCV) circuit, specifically related to the proportional solenoid control signal.

This code triggers when the ECM detects an open circuit, short to ground, or voltage irregularity in the electrical pathway controlling one of the hydraulic system's proportional solenoid valves. On the DX150LC-9C excavator, these solenoids regulate hydraulic flow to critical functions like boom, arm, and swing operations. The Doosan D34 engine relies on precise electronic communication between the engine controller and hydraulic system to optimize fuel efficiency and hydraulic response. When this circuit fails, the machine may enter a protective derate mode to prevent damage to hydraulic components or electrical systems.

This fault is particularly critical because it directly affects the excavator's primary work functions, potentially causing significant downtime on job sites.

Common Symptoms

• Hydraulic Function Loss: Specific hydraulic functions (boom, arm, bucket, or swing) may operate sluggishly, intermittently, or not respond at all
• Warning Indicators: Engine malfunction light illuminates on the instrument cluster; fault code displays on the monitor panel
• Engine Derate: Engine power may be reduced to 75-80% capacity as a protective measure
• Erratic Hydraulic Response: Hydraulic movements may be jerky or unpredictable, especially under load
• Intermittent Operation: Symptoms may appear and disappear, particularly when machine vibrates or operates on uneven terrain

Potential Causes

In used DX150LC-9C excavators, this fault code typically stems from:

• Wiring Harness Damage: The harness running from the ECM (located near the battery box) to the main control valve experiences rubbing against the swing motor housing or frame—a known wear point on 2015-2018 models
• Connector Corrosion: The 12-pin Deutsch connector at the MCV often accumulates moisture and dirt, causing resistance issues
• Solenoid Coil Failure: The proportional solenoid coils themselves can develop internal short circuits or open windings after 5,000+ operating hours
• ECM Voltage Supply Issues: Degraded battery connections or failing alternators causing voltage fluctuations below 22V (on 24V systems)
• Damaged ECM Pin Terminals: Corrosion or bent pins in the ECM connector from previous repair attempts

How to Troubleshoot and Fix Code E520708-12

Step 1: Initial Inspection and Data Retrieval

Connect Doosan DMS-5 diagnostic software or a compatible CANbus scanner to retrieve freeze frame data. Note the specific solenoid circuit identified (boom, arm, bucket, or swing). Perform a visual inspection of the entire wiring harness from ECM to MCV, checking for obvious abrasions, cuts, or pinch points where the harness crosses the swing bearing area.

Step 2: Electrical Testing at the Main Control Valve

Disconnect the 12-pin connector at the hydraulic main control valve. Inspect for green corrosion, bent pins, or moisture intrusion—extremely common in used machines. Using a digital multimeter, measure resistance across the suspected solenoid coil terminals (typically pins 3-4, 5-6, 7-8, or 9-10 depending on function). Specification should be 8-12 ohms at room temperature. Readings below 5 ohms indicate a short; infinite resistance indicates an open coil.

Step 3: Harness Continuity and Voltage Supply Check

With the connector still disconnected at the MCV, check continuity from each pin back to the corresponding ECM terminal. There should be less than 1 ohm resistance. Check for shorts to ground by measuring resistance between each wire and chassis ground (should read infinite/OL). Reconnect the harness and check for supply voltage from the ECM with the key on, engine off—should read approximately 5-12V DC depending on solenoid type.

Step 4: Used Equipment Specific Checks

On used excavators, inspect the swing post area where the harness passes through the rotating joint. This is a critical wear point where constant rotation causes wire fatigue. Look for harness ties that have broken, allowing wires to contact metal surfaces. Check the ECM ground connections at the battery and frame—corrosion here causes voltage irregularities that mimic solenoid failures.

Step 5: Component Replacement and Verification

If testing confirms a failed solenoid coil, replace the specific proportional solenoid cartridge (Doosan part number varies by function). If harness damage is found, repair using 16-18 AWG marine-grade wire with heat-shrink solder connections—avoid crimp connectors in high-vibration areas. After repairs, clear codes using diagnostic software, operate all hydraulic functions through full range of motion, and verify the code does not return.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Doosan service manual for your specific serial number range and follow proper lockout/tagout procedures. If unfamiliar with high-voltage electrical systems or hydraulic troubleshooting, consult a certified Doosan technician to avoid injury or further equipment damage.