What is Sumitomo SH210LC-5LR Fault Code 112?

Fault Code 112 on the Sumitomo SH210LC-5LR indicates a Main Relief Valve Solenoid Circuit Malfunction. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal electrical condition in the circuit controlling the main relief valve solenoid, which regulates maximum system hydraulic pressure.

The main relief valve solenoid is critical for protecting the hydraulic system from over-pressurization during heavy digging or lifting operations. When this circuit malfunctions, the ECM cannot properly modulate hydraulic pressure, potentially leading to reduced machine performance, component damage, or unsafe operating conditions. On used SH210LC-5LR excavators, this code frequently appears due to age-related electrical degradation or hydraulic contamination affecting solenoid operation.

Common Symptoms

When Code 112 is active, operators typically experience:

• Illuminated warning lamp on the instrument cluster with reduced engine power
• Loss of hydraulic power or inconsistent boom/arm movement during operation
• Unusual hydraulic system noises such as excessive relief valve chattering or whining
• Intermittent performance issues that worsen as hydraulic oil temperature increases
• Machine entering derate mode limiting engine RPM to protect hydraulic components

Potential Causes

The most common technical reasons for Code 112 on used SH210LC-5LR excavators include:

• Faulty main relief valve solenoid due to internal coil failure or contamination from degraded hydraulic fluid
• Damaged wiring harness near the hydraulic pump area where cables experience vibration and heat exposure
• Corroded or loose electrical connectors at the solenoid or ECM interface points
• Short circuit or open circuit in the solenoid control wiring caused by harness rubbing against frame components
• ECM internal fault affecting the solenoid driver circuit (less common but possible in high-hour machines)
• Low battery voltage or poor ground connections affecting solenoid energization

How to Troubleshoot and Fix Code 112

Step 1: Visual Inspection Begin by inspecting the main relief valve solenoid located on the main hydraulic pump. Check for physical damage, oil contamination on electrical connections, or damaged connector pins. Examine the wiring harness from the solenoid to the ECM for signs of abrasion, melting, or damage at known rub points near the swing motor and pump mounting area.

Step 2: Electrical Testing Using a digital multimeter, measure solenoid coil resistance (typically 10-15 ohms for Sumitomo solenoids). Disconnect the solenoid connector and check for continuity and proper resistance values. Test for voltage supply at the connector with ignition on (should show battery voltage). Inspect harness continuity between the solenoid and ECM pins according to the service manual wiring diagram.

Step 3: Component Testing and Replacement If electrical values are correct, perform a functional test by swapping the suspect solenoid with a known-good unit if available. For used excavators, always clean connector terminals with electrical contact cleaner and apply dielectric grease before reconnection. Clear the fault code using Sumitomo diagnostic software and perform a system pressure test to verify proper relief valve operation (typically 320-350 bar).

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical or hydraulic issues.