Komatsu PC200-8E0 Fault Code E-27: Comprehensive Diagnostic Guide

What is Komatsu PC200-8E0 Fault Code E-27?

Fault Code E-27 indicates a malfunction in the hydraulic pump control system, specifically related to the pump discharge pressure sensor circuit or abnormal pressure readings detected by the machine's Electronic Control Module (ECM).

This code triggers when the ECM detects voltage signals outside the normal operating range from the main pump discharge pressure sensor. On the PC200-8E0, this sensor is critical for monitoring hydraulic system performance and enabling the machine's advanced flow control features. The ECM uses this data to optimize pump output, prevent overload conditions, and maintain efficient fuel consumption. When E-27 activates, the machine may enter a protective derate mode to prevent catastrophic hydraulic system damage.

Common Symptoms

When Code E-27 is active, operators typically experience:

• Hydraulic system derate with noticeably reduced digging force and slower cycle times
• Warning light illumination on the monitor panel, often accompanied by an audible alarm
• Erratic boom or arm movement due to inconsistent pressure readings affecting flow compensation
• Intermittent code activation during high-load operations like heavy digging or lifting
• Poor fuel efficiency as the ECM cannot properly optimize pump displacement

Potential Causes

The most common technical reasons for E-27 on used PC200-8E0 excavators include:

• Faulty pressure sensor (Part #: 7861-93-1651) due to internal diaphragm failure or contamination
• Damaged sensor wiring harness at common rub points near the hydraulic pump mounting bracket
• Corroded or loose electrical connectors at the sensor or ECM interface (particularly the 3-pin Deutsch connector)
• Contaminated hydraulic oil causing sensor port blockage or incorrect pressure readings
• ECM calibration drift in older machines with high operating hours (8,000+ hours)
• Intermittent short circuits caused by pinched wires in the main chassis harness bundle

How to Troubleshoot and Fix Code E-27

Step 1: Visual Inspection and Preliminary Checks

Begin by locating the main pump discharge pressure sensor mounted on the hydraulic pump assembly. Inspect the 3-pin connector for corrosion, bent pins, or hydraulic oil contamination—common in used excavators operating in wet conditions. Check the wiring harness for abrasion damage where it passes near the pump mounting bracket and swing bearing areas.

Step 2: Electrical Testing with Diagnostic Tools

Using a digital multimeter, backprobe the sensor connector with the key ON/engine OFF. Verify the 5-volt reference voltage from the ECM (Pin 1). Check sensor ground continuity (Pin 2) and measure the signal voltage (Pin 3), which should read 0.5-4.5 volts depending on system pressure. Resistance across sensor terminals should measure 250-350 ohms at room temperature. Connect Komatsu KOMTRAX diagnostic software to read live pressure data and compare against mechanical gauge readings.

Step 3: Component Testing and Repair

If electrical values are correct but the code persists, install a mechanical pressure gauge in the test port to verify actual hydraulic pressure versus sensor output. On used machines, remove the sensor and inspect the threaded port for metal debris or contamination. Test the new or suspect sensor on the bench by applying regulated air pressure while monitoring voltage output. Replace the complete wiring harness if insulation damage is found, as repairs often fail in high-vibration environments.

Step 4: System Verification and Reset

After repairs, clear fault codes using the diagnostic software. Perform a full hydraulic cycle test under load conditions. Monitor live sensor data during operation to confirm stable readings between 280-350 bar during maximum demand. For excavators with 5,000+ hours, consider replacing the sensor proactively even if current readings appear normal, as sensor drift is common.

---

Disclaimer: This guide provides general diagnostic information for Code E-27. Hydraulic system repairs involve high-pressure components and specialized tools. Always consult the official Komatsu service manual and consider professional diagnostic support for complex electrical issues or if you lack proper testing equipment.