Sumitomo SH350HD-6 Fault Code 1112: Complete Diagnostic Guide

What is Sumitomo SH350HD-6 Fault Code 1112?

Fault Code 1112 indicates a fuel injection timing solenoid valve circuit malfunction in the Sumitomo SH350HD-6 excavator's electronic control system. This code specifically signals that the Engine Control Module (ECM) has detected an abnormal voltage or resistance reading in the circuit controlling the fuel injection timing valve, which precisely regulates fuel delivery timing to optimize combustion efficiency.

This fault is critical for the SH350HD-6 because improper fuel injection timing directly impacts engine performance, fuel economy, and emissions compliance. The Isuzu 6WG1X engine powering this excavator relies on precise electronic fuel injection control to deliver its rated 257 horsepower efficiently. When Code 1112 activates, the ECM typically enters a protective limp mode to prevent potential engine damage.

Common Symptoms

When Code 1112 is active on your SH350HD-6, operators typically experience:

• Check Engine Light illuminated on the instrument panel with possible warning buzzer activation
• Noticeable power loss or engine derating, particularly under heavy load conditions
• Rough idling or inconsistent engine RPM fluctuations at low throttle settings
• Black or gray exhaust smoke indicating incomplete combustion due to timing issues
• Difficulty starting the engine, especially during cold starts or after extended shutdown periods

Potential Causes

The most common technical causes for Code 1112 in used SH350HD-6 excavators include:

• Faulty fuel injection timing solenoid valve due to internal coil failure or mechanical sticking (common after 8,000+ operating hours)
• Damaged wiring harness along the engine valley where heat and vibration cause insulation breakdown
• Corroded or loose electrical connectors at the solenoid valve or ECM interface points
• ECM power supply issues including poor ground connections or voltage fluctuations
• Failed ECM internal driver circuit that controls solenoid valve operation
• Contaminated fuel system causing solenoid valve deposits and restricted movement

How to Troubleshoot and Fix Code 1112

Step 1: Visual Inspection and Connector Check Begin by thoroughly inspecting the fuel injection timing solenoid valve located on the high-pressure fuel pump assembly. Check the electrical connector for corrosion, bent pins, or moisture intrusion—common issues in used excavators operating in dusty or wet conditions. Clean connectors with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 2: Electrical Circuit Testing Using a digital multimeter, measure the solenoid valve resistance. Disconnect the valve connector and check resistance across the solenoid terminals; typical specifications range from 2-6 ohms (consult your service manual for exact values). Next, perform a voltage supply test with the key on, engine off—you should read battery voltage (approximately 24V) at the connector. Check for continuity to ground in the wiring harness, as shorts to ground are frequent failure points.

Step 3: Harness and ECM Verification Trace the wiring harness from the solenoid valve to the ECM, paying special attention to areas where the harness contacts hot engine components or sharp metal edges. In used SH350HD-6 machines, harness chafing near the fuel filter bracket is a known wear point. If wiring and solenoid test within specifications, connect Sumitomo diagnostic software (or compatible scan tool) to check ECM outputs and verify the controller can properly energize the circuit. Replace the ECM only after confirming all other components test correctly.

Disclaimer: This guide provides general troubleshooting information for Code 1112. Always consult the official Sumitomo service manual for your specific machine serial number and software version. If you're uncertain about electrical diagnostics or fuel system work, consult a certified heavy equipment technician to prevent costly misdiagnosis or safety hazards.