What is Doosan DX150LC-9C Fault Code E000735-06?

Fault Code E000735-06 indicates an Engine Oil Pressure Sensor Circuit Low Voltage condition on the Doosan DX150LC-9C excavator. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects a voltage signal from the engine oil pressure sensor that falls below the manufacturer's specified threshold, typically under 0.5 volts.

This code directly affects the engine protection system on the DX150LC-9C. The oil pressure sensor monitors lubricant flow to critical engine components, and when the ECM cannot reliably read this data due to low voltage, it may initiate protective measures including power derate or shutdown to prevent catastrophic engine damage. For used excavators, this fault is particularly critical as it can indicate either legitimate oil pressure issues or electrical degradation common in aging machines.

Common Symptoms

When fault code E000735-06 is active, operators typically experience:

• Check Engine Light or malfunction indicator lamp illuminated on the instrument cluster
• Engine derate mode activated, limiting maximum RPM to approximately 1500-1800 RPM
• Audible warning alarm sounding intermittently or continuously
• Reduced hydraulic performance due to limited engine power output
• Potential engine shutdown if the ECM determines oil pressure data is unreliable during operation

Potential Causes

The most common technical causes for E000735-06 on used DX150LC-9C excavators include:

• Oil pressure sensor failure due to internal circuit degradation or contamination
• Damaged sensor wiring harness particularly at flex points near the engine block where vibration causes wire chafing
• Corroded or loose electrical connectors at the sensor or ECM connection points
• Short circuit to ground in the sensor signal wire from harness rubbing against frame components
• Low actual engine oil pressure causing legitimate sensor readings that appear as electrical faults
• ECM internal circuit failure (less common but possible in high-hour machines)

How to Troubleshoot and Fix Code E000735-06

Step 1: Visual Inspection and Preliminary Checks

Begin by verifying actual engine oil level and condition. Low or contaminated oil can cause legitimate pressure drops. Inspect the oil pressure sensor (located on the engine block near the oil filter housing) and its connector for obvious damage, corrosion, or oil contamination. On used excavators, pay special attention to the wiring harness routing from the sensor to the ECM—look for worn insulation, exposed wires, or evidence of rubbing against metal surfaces.

Step 2: Electrical Testing

Using a digital multimeter, disconnect the oil pressure sensor connector and measure the resistance across the sensor terminals. Compare readings to Doosan specifications (typically 50-250 ohms at ambient temperature). Check for continuity to ground on the signal wire with the sensor disconnected—any continuity indicates a short circuit. Measure voltage supply from the ECM at the connector (should be approximately 5 volts reference voltage).

Step 3: Sensor Replacement and Harness Repair

If electrical tests reveal sensor failure, replace the oil pressure sensor with a genuine Doosan or OEM-equivalent part. Before installation, inspect the sensor mounting port for debris or damage. If wiring issues are identified, repair or replace the affected harness section, ensuring proper routing away from heat sources and moving components. For used machines, consider applying dielectric grease to connectors and securing harnesses with new protective loom and zip ties. After repairs, clear the fault code using Doosan diagnostic software (DMS) or a compatible scan tool, and perform an operational test under load to verify the repair.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Doosan service manual for your specific machine serial number and seek professional assistance from certified Doosan technicians for complex repairs or if you're unsure about any procedure.