What is Komatsu PC220-7 Fault Code E205?

Fault Code E205 on the Komatsu PC220-7 indicates a malfunction in the Engine Control Module (ECM) communication circuit with the hydraulic system's pressure sensor. Specifically, this code triggers when the ECM detects an abnormal signal or complete loss of communication from the main hydraulic pump pressure sensor, which monitors system pressure to optimize engine output and hydraulic performance.

This code is critical for the PC220-7 because the ECM relies on accurate pressure data to regulate engine speed, prevent overload conditions, and protect hydraulic components. When communication fails, the machine may enter a derated performance mode to prevent potential damage, significantly reducing productivity on job sites. For used excavators, this code often signals age-related sensor degradation or wiring issues common in machines with 8,000+ operating hours.

Common Symptoms

• Yellow hydraulic warning light illuminated on the instrument cluster, sometimes accompanied by an audible alarm
• Noticeable loss of hydraulic power during digging or lifting operations, particularly under heavy loads
• Engine automatically derates to lower RPM (typically 1,400-1,600 RPM) regardless of throttle position
• Intermittent code activation that clears and returns, especially when operating on uneven terrain or during temperature changes
• Sluggish boom and arm response with delayed hydraulic function engagement

Potential Causes

The most common technical causes for E205 on used PC220-7 excavators include:

• Failed main hydraulic pressure sensor due to internal diaphragm fatigue or electrical component breakdown (extremely common after 6,000+ hours)
• Corroded or loose connector pins at the sensor harness connection point near the hydraulic pump
• Damaged wiring harness between the ECM and pressure sensor, particularly where the harness contacts the engine block or runs along the main pump housing (known rub point on this model)
• Contaminated sensor connector from hydraulic oil mist or moisture intrusion in the engine compartment
• ECM internal fault (rare, but possible in high-hour machines with voltage spike history)
• Poor ground connection at the sensor mounting bracket or ECM ground points

How to Troubleshoot and Fix Code E205

Step 1: Visual Inspection Begin by locating the main hydraulic pressure sensor on the pump housing (driver's side, near the center joint). Inspect the electrical connector for oil contamination, corrosion on pins, or physical damage. Check the wiring harness routing for visible wear, especially where it contacts metal surfaces. For used excavators, carefully examine areas where previous repairs may have altered harness positioning.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check sensor resistance. The PC220-7 pressure sensor should read approximately 250-350 ohms at room temperature (consult your service manual for exact specifications). Check continuity between the sensor signal wire (typically green/white) and ECM Pin #27 for opens or high resistance above 5 ohms. Measure supply voltage at the connector with ignition on—it should read 4.8-5.2 volts DC.

Step 3: Sensor and Harness Replacement If resistance or voltage readings are out of specification, replace the hydraulic pressure sensor (Komatsu part #7861-93-1651 or equivalent). Before installation, clean the mounting threads and apply appropriate thread sealant. If wiring shows damage, replace the affected harness section and re-route away from heat sources and moving components. After repairs, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then run the machine through full hydraulic cycles to verify repair.

Step 4: Verify Repair Operate the excavator under normal working loads for 15-20 minutes while monitoring for code recurrence. For used machines, pay particular attention during the first heat cycle, as intermittent connection issues may only appear after thermal expansion.

---

Disclaimer: This guide provides general troubleshooting information for the Komatsu PC220-7. Always consult the official Komatsu service manual for your specific serial number and software version. If you lack proper diagnostic tools or experience with hydraulic systems, consult a certified Komatsu technician to prevent injury or further machine damage.