Komatsu PC800-7 Fault Code E936: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E936?

Fault Code E936 indicates a malfunction in the hydraulic pump control system, specifically related to the pump flow control solenoid valve circuit or its associated sensors. This code is triggered when the Electronic Control Module (ECM) detects an abnormal voltage, current draw, or response time from the pump control solenoid that regulates hydraulic flow distribution.

In the PC800-7, this system is critical for maintaining optimal hydraulic performance across all functions. The pump flow control solenoid adjusts displacement based on load demands, directly affecting fuel efficiency and operational responsiveness. When E936 activates, the machine typically enters a protective derate mode to prevent hydraulic system damage.

Common Symptoms

When Code E936 is active, operators typically experience:

• Reduced hydraulic power across all functions (boom, arm, bucket, swing)
• Illuminated warning lamp on the monitor panel with fault code display
• Sluggish or unresponsive controls, particularly under heavy load conditions
• Inconsistent hydraulic response or jerky movements during combined operations
• Increased fuel consumption due to inefficient pump regulation

Potential Causes

The most common technical causes for E936 on used PC800-7 excavators include:

• Solenoid valve coil failure due to overheating or internal short circuits
• Wiring harness damage at known rub points near the hydraulic pump mounting area
• Corroded or loose connector pins at the pump control solenoid (common in high-hour machines)
• ECM internal fault affecting the solenoid driver circuit
• Contaminated hydraulic oil causing solenoid valve sticking or sluggish response
• Voltage supply issues from damaged power supply wiring or poor ground connections

How to Troubleshoot and Fix Code E936

Step 1: Visual Inspection Begin by inspecting the pump control solenoid connector for corrosion, bent pins, or moisture intrusion. On used excavators, check the wiring harness routing near the hydraulic pump for abrasion points where the harness contacts the frame or pump housing.

Step 2: Electrical Testing Using a digital multimeter, measure solenoid coil resistance (typically 3-7 ohms for Komatsu solenoids). Check supply voltage at the connector with ignition on (should read 24V DC). Verify ground circuit continuity with less than 1 ohm resistance.

Step 3: Dynamic Testing Connect Komatsu diagnostic software (KOMTRAX Plus) to monitor real-time solenoid command signals versus actual response. Compare current draw during activation (typically 2-4 amps). Excessive current indicates internal solenoid short; no current suggests open circuit or ECM driver failure.

Step 4: Component Replacement If electrical tests confirm solenoid failure, replace the valve assembly and thoroughly clean the connector with electrical contact cleaner. For used machines, always replace connector seals to prevent future moisture issues.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual and consider professional assistance for complex electrical diagnostics or hydraulic system repairs.