Komatsu PC50MR-2 Fault Code E-6: Complete Diagnostic Guide

What is Komatsu PC50MR-2 Fault Code E-6?

Fault Code E-6 on the Komatsu PC50MR-2 indicates a malfunction in the hydraulic pump pressure sensor circuit or abnormal hydraulic system pressure detection. This code triggers when the Electronic Control Module (ECM) detects voltage irregularities from the main hydraulic pump pressure sensor or when system pressure readings fall outside manufacturer-specified parameters.

This fault is critical for the PC50MR-2 because it directly affects the machine's ability to regulate hydraulic pump output and optimize fuel efficiency. When this sensor circuit fails, the excavator cannot properly adjust pump displacement, leading to reduced performance and potential component damage from uncontrolled pressure spikes.

Common Symptoms

When Code E-6 is active, operators typically experience:

• Intermittent or constant warning light on the instrument panel indicating hydraulic system issues
• Reduced hydraulic power across all functions (boom, arm, bucket, swing)
• Erratic or sluggish machine response during operation, especially under load
• Unusual hydraulic pump noise or whining due to improper pressure regulation
• Increased fuel consumption as the ECM defaults to maximum pump displacement in fail-safe mode

Potential Causes

The most common technical reasons for E-6 fault code activation include:

• Hydraulic pressure sensor failure due to internal diaphragm wear or contamination (common in machines with 4,000+ operating hours)
• Corroded or damaged wiring harness between sensor and ECM, particularly at connector pins near the pump mounting area
• Loose or oil-contaminated electrical connections at the sensor plug (typical on used equipment exposed to hydraulic fluid leaks)
• Physical damage to sensor mounting threads causing pressure signal distortion from vibration
• ECM software glitches or voltage supply issues from aging electrical components
• Hydraulic oil contamination affecting sensor accuracy through particulate buildup on sensor face

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Begin by inspecting the hydraulic pump pressure sensor located on the main pump body. Check for hydraulic oil leaks around the sensor, damaged wiring, or corroded connector pins. On used excavators, pay special attention to harness routing where it contacts metal brackets—friction wear is common on the PC50MR-2 at approximately 3,500 hours.

Step 2: Electrical Testing Using a digital multimeter, verify sensor power supply voltage (should read 4.8-5.2V DC with ignition on). Check sensor ground continuity to chassis. Measure sensor signal output voltage while engine idles—expect 0.5-4.5V depending on pressure. Compare readings against Komatsu specifications in the service manual.

Step 3: Sensor and Connection Service Disconnect the sensor connector and clean terminals with electrical contact cleaner. Inspect for bent pins or corrosion (replace connector if damaged). Remove sensor and check mounting threads for cross-threading or metal debris. Replace sensor if resistance values deviate from spec (typically 250-350 ohms at room temperature).

Step 4: System Verification Clear codes using Komatsu diagnostic software (KOMTRAX) or aftermarket scan tools. Operate machine through full hydraulic cycle. Monitor live data for pressure fluctuations. If code returns immediately, inspect ECM connections and verify hydraulic system pressure with mechanical gauge to rule out actual pressure problems versus sensor issues.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu service manual for your specific serial number and operating conditions. If unfamiliar with hydraulic systems or electrical diagnostics, consult a certified Komatsu technician to prevent equipment damage or personal injury.