What is Doosan Excavator Fault Code E000651-31?

Fault Code E000651-31 indicates a hydraulic system pressure sensor circuit malfunction, specifically detecting an abnormal voltage signal from the main pump pressure sensor. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) receives voltage readings outside the expected range (typically below 0.5V or above 4.5V) from the main hydraulic pump pressure transducer.

In Doosan excavators, the main pump pressure sensor plays a critical role in monitoring hydraulic system performance and enabling the Electronic Power Optimizing System (EPOS) to adjust pump output based on load demand. When this sensor circuit fails, the machine cannot properly regulate hydraulic flow, leading to reduced efficiency, potential overheating, and compromised digging performance. For used excavators, this code often signals age-related sensor degradation or harness damage from continuous vibration and exposure.

Common Symptoms

• Hydraulic system warning light illuminated on the instrument cluster with reduced machine responsiveness
• Loss of hydraulic power during high-demand operations like digging or lifting heavy loads
• Erratic boom or arm movements with inconsistent speed control across work functions
• Engine derating or automatic power reduction to protect hydraulic components from damage
• Increased hydraulic oil temperature due to improper pump regulation and flow compensation

Potential Causes

The most common technical causes for E000651-31 in used Doosan excavators include:

• Failed main pump pressure sensor due to internal component wear, seal deterioration, or diaphragm damage (common after 5,000+ operating hours)
• Damaged sensor wiring harness at known rub points near the pump mounting area or along the main boom pivot
• Corroded or loose electrical connectors at the sensor plug or ECM interface, particularly on machines operating in wet or corrosive environments
• Short circuit or open circuit in the sensor signal wire caused by rodent damage or harness chafing
• ECM internal fault affecting the analog-to-digital converter circuit (rare, but possible in high-hour machines)
• Contaminated hydraulic oil causing sensor membrane fouling and inaccurate pressure readings

How to Troubleshoot and Fix Code E000651-31

Step 1: Visual Inspection Begin by locating the main pump pressure sensor (typically mounted on the hydraulic pump housing). Inspect the wiring harness from sensor to ECM for visible damage, abrasion, or oil contamination. Check connector pins for corrosion, bent terminals, or moisture intrusion—critical on used equipment.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure supply voltage at the ECM side (should read approximately 5V with ignition on). Check signal wire resistance to ground (should show open circuit/infinite resistance). Measure sensor output voltage while applying known hydraulic pressure or use a pressure simulator tool to verify sensor response curve.

Step 3: Sensor and Circuit Validation If voltage readings are correct but code persists, substitute the pressure sensor with a known-good unit. Clear codes using Doosan DX-DIAG diagnostic software and perform a functional test under load. If the replacement sensor resolves the issue, inspect the old sensor for physical damage or internal failure. For intermittent codes on used machines, thoroughly inspect harness routing for wear points and secure with proper abrasion-resistant sleeving.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Doosan service manual for your specific model and seek professional assistance for complex electrical diagnostics or hydraulic system repairs.