Sumitomo SH260LC-6 Fault Code 122: Complete Diagnostic Guide

What is Sumitomo SH260LC-6 Fault Code 122?

Fault Code 122 on the Sumitomo SH260LC-6 indicates a Main Pump 1 Regulator Solenoid Circuit Malfunction. This code specifically signals an electrical issue within the circuit controlling the primary hydraulic pump's regulator solenoid valve, which manages pump displacement and system pressure.

The main pump regulator solenoid plays a critical role in the SH260LC-6's hydraulic load-sensing system. When the ECM (Engine Control Module) detects abnormal voltage, current draw, or an open/short circuit in this solenoid's wiring, it triggers Code 122. This fault directly impacts hydraulic performance, as the pump cannot properly adjust flow based on load demands, leading to inefficient operation and potential damage to hydraulic components.

Common Symptoms

When Code 122 is active on your SH260LC-6, operators typically experience:

• Reduced hydraulic power across all functions, particularly during simultaneous operations
• Erratic boom or arm movement with inconsistent speed and responsiveness
• Warning light illumination on the instrument cluster, often accompanied by audible alarms
• Engine over-revving without corresponding hydraulic work output due to improper pump regulation
• Increased fuel consumption as the system cannot efficiently match pump output to load requirements

Potential Causes

For used excavators like the SH260LC-6, this fault commonly stems from:

• Damaged wiring harness near the main pump mounting area, where vibration and heat cause insulation breakdown
• Corroded or loose connector pins at the solenoid or ECM connections, especially in machines exposed to wet conditions
• Failed regulator solenoid coil due to age-related internal short circuits or open windings
• Chafed wires at known rub points along the frame rail between the cab and pump compartment
• ECM internal driver circuit failure, though less common than external wiring issues

How to Troubleshoot and Fix Code 122

Step 1: Visual Inspection Begin by examining the entire wiring harness from the ECM to the main pump regulator solenoid. On used SH260LC-6 excavators, inspect where the harness passes near the swing bearing and hydraulic lines—common wear points. Look for abraded insulation, pinched wires, or burnt connectors.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure resistance across the solenoid coil terminals. Typical specification is 10-15 ohms at room temperature. Check for voltage supply (typically 12V) at the harness connector with ignition on. Test for shorts to ground on both circuit wires.

Step 3: Connector and Ground Verification Clean all connector pins with electrical contact cleaner and inspect for corrosion (green/white deposits common in older machines). Verify the ground circuit has less than 0.5 ohms resistance to chassis ground. Replace any damaged connectors with OEM-quality parts.

Step 4: Component Replacement If wiring tests normal, replace the regulator solenoid valve. For used excavators, always inspect the solenoid mounting area for oil contamination that may have damaged the coil. After replacement, clear codes using Sumitomo diagnostic software or compatible scan tool and perform operational testing under load.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or create safety hazards.