What is Doosan DX150 Fault Code P068A?

Fault Code P068A indicates an ECM/PCM Power Relay De-Energized Performance problem, meaning the engine control module has detected an issue with the main power relay circuit that supplies voltage to critical control systems. This diagnostic trouble code (DTC) is triggered when the ECM (Engine Control Module) detects that the power relay has unexpectedly lost power or is cycling on and off during operation, compromising the machine's ability to maintain consistent electronic control over fuel injection, timing, and emissions systems.

For the Doosan DX150 excavator, this fault is particularly critical because the power relay serves as the gateway for all electrical power distribution to the engine management system. When this relay malfunctions, the machine may experience sudden shutdowns, intermittent starting issues, or complete loss of electronic engine control, directly impacting job site productivity and potentially causing unsafe operating conditions.

Common Symptoms

• Intermittent or complete engine shutdown without warning, often occurring after the machine has warmed up
• Check Engine light illuminated on the instrument cluster, sometimes accompanied by a main power warning indicator
• Difficulty starting the engine, requiring multiple key cycles before the excavator fires up
• Loss of electronic throttle response or sudden engine derating to limited RPM ranges
• Electrical accessories cutting out momentarily, including dash display flickering or hydraulic control system interruptions

Potential Causes

The most common technical reasons for Code P068A on used Doosan DX150 excavators include:

• Failed main power relay located in the fuse/relay panel, often due to contact wear from repeated thermal cycling over thousands of operating hours
• Corroded or loose connections at the relay socket or ECM power supply harness, particularly common in machines exposed to moisture or coastal environments
• Damaged wiring harness between the battery, relay panel, and ECM—inspect for rubbing points near the engine mount brackets and along the right-side frame rail where harnesses pass through grommets
• Weak battery or poor ground connections causing voltage drops below the ECM's minimum operating threshold (typically below 9.5 volts during cranking)
• ECM internal power supply circuit failure, less common but possible in high-hour machines (5,000+ hours)

How to Troubleshoot and Fix Code P068A

Step 1: Perform Initial Visual Inspection Start by inspecting the main fuse and relay panel, typically located under the operator's cab or behind the right-side access panel. Check for corrosion, burnt contacts, or signs of water intrusion. Remove the main power relay (consult your service manual for exact location—usually a larger 4 or 5-pin relay) and inspect the terminals for pitting or discoloration.

Step 2: Test Electrical Circuits with Diagnostic Tools Using a digital multimeter, verify battery voltage at rest (should read 12.4-12.8V) and during cranking (shouldn't drop below 9.5V). With the key in the "ON" position (engine off), measure voltage at the relay coil terminals—you should see battery voltage. Next, check for continuity through the relay itself using the multimeter's ohm setting; a functional relay shows 50-120 ohms across coil terminals. Test the power output circuit from the relay to the ECM; it should show full battery voltage when the relay is energized.

Step 3: Inspect Harness and Connections Specific to Used Equipment For used excavators, pay special attention to harness wear points: trace the main power harness from the relay panel to the ECM connector (typically mounted on the engine block or firewall). Look for chafing against sharp edges, particularly where harnesses pass through metal grommets or near hydraulic lines. Disconnect the ECM main power connector and inspect pins for corrosion, bent terminals, or moisture. Clean all connections with electrical contact cleaner and apply dielectric grease before reassembly.

Step 4: Replace Components and Clear Code If testing reveals a faulty relay, replace it with a genuine Doosan part or high-quality equivalent matching the original amperage rating (typically 30-40A for this application). If wiring damage is found, repair using OEM-spec wire and heat-shrink connectors—avoid simple crimp splices on power circuits. After repairs, clear the fault code using Doosan G-Scan diagnostic software or a compatible scan tool, then run the machine through a complete warm-up cycle to verify the fix.

---

Disclaimer: This guide provides general troubleshooting information for educational purposes. Always consult the official Doosan service manual for your specific machine serial number, and consider engaging a certified heavy equipment technician for complex electrical diagnostics. Improper electrical repairs can cause serious machine damage or safety hazards.