What is Komatsu PC300-7 Fault Code E113?

Komatsu PC300-7 fault code E113 indicates a "Main Relief Valve Solenoid Circuit Malfunction" in the hydraulic system's electronic control circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal voltage or current flow in the electrical circuit controlling the main relief valve solenoid, which regulates maximum hydraulic system pressure.

This fault is critical for the PC300-7 because the main relief valve protects the hydraulic pump and circuit from over-pressurization. When the solenoid control circuit fails, the machine cannot properly modulate system pressure, potentially leading to reduced digging force, erratic hydraulic functions, or complete hydraulic system shutdown. For used excavators, this code often points to age-related electrical degradation rather than mechanical valve failure.

Common Symptoms

• Yellow warning lamp illuminated on the instrument cluster with E113 displayed on the monitor panel
• Reduced hydraulic power across all functions (boom, arm, bucket, swing) due to system entering protective derate mode
• Inconsistent hydraulic response, particularly when multiple functions are operated simultaneously under heavy load
• Intermittent activation where the code appears during warm-up or after extended operation (indicating heat-related electrical issues)
• Machine may enter limp mode, restricting engine RPM to approximately 1,500 to protect hydraulic components

Potential Causes

The most common technical causes for E113 on used PC300-7 excavators include:

• Damaged solenoid wiring harness at known wear points near the main control valve assembly where vibration causes insulation breakdown
• Corroded or loose connector pins at the relief valve solenoid plug (especially on machines operated in marine or corrosive environments)
• Failed main relief valve solenoid coil, typically showing open circuit resistance instead of the specified 10-15 ohms
• ECM power supply issues affecting the 12V switched output to hydraulic solenoids
• Grounding problems at chassis ground points G103 or G104, which serve hydraulic control circuits on this model
• Rarely, ECM internal driver failure on the solenoid output circuit board

How to Troubleshoot and Fix Code E113

Step 1: Visual Inspection and Connector Check Locate the main relief valve solenoid on the main control valve (MCV) assembly beneath the operator platform. Disconnect the 2-pin connector and inspect for corrosion, pushed-back pins, or moisture intrusion. On used machines, check the wiring harness routing for abrasion points where it contacts the valve body or frame—this is a notorious failure point on PC300-7 models with over 5,000 hours.

Step 2: Electrical Testing with Multimeter With the connector disconnected and ignition off, measure solenoid coil resistance across the two terminals. You should read 10-15 ohms at room temperature. An open circuit (infinite resistance) indicates coil failure. Next, check for voltage supply at the harness connector with ignition on: you should see battery voltage (12-14V). Use a test light or voltmeter to confirm the ECM is commanding the solenoid during system activation.

Step 3: Ground Circuit and Harness Continuity Verify ground continuity from the solenoid ground wire to chassis ground (should be less than 1 ohm). Trace the harness back to the ECM connector (typically located under the cab floor) and check for voltage drop exceeding 0.5V, which indicates corroded splices or damaged conductors. For persistent issues on used excavators, inspect harness routing and secure any sections making contact with sharp edges.

Step 4: Component Replacement and Validation If testing confirms solenoid failure, replace the main relief valve solenoid (Komatsu part number typically 723-46-13200 or equivalent). After replacement, clear codes using Komatsu diagnostic software (KTMS or compatible scan tool) and perform a hydraulic system pressure test to verify proper relief valve operation at specified 350-360 bar (5,075-5,220 PSI).

Disclaimer: This guide provides general troubleshooting information. Always consult the Komatsu PC300-7 service manual for complete diagnostic procedures and torque specifications. If uncertain, engage a certified Komatsu technician to prevent further damage to hydraulic or electrical systems.