What is Sumitomo SH220LC-6 Fault Code 651?

Fault Code 651 on the Sumitomo SH220LC-6 excavator indicates a malfunction in the hydraulic pump solenoid circuit, specifically related to abnormal voltage or current flow in the pump control system. This diagnostic trouble code (DTC) is generated by the machine's Electronic Control Module (ECM) when it detects irregular electrical signals from the proportional solenoid valve that regulates hydraulic pump displacement and flow.

This code is critical because the hydraulic pump is the heart of your excavator's performance. The pump solenoid directly controls engine load sensing and hydraulic output, affecting everything from swing speed to digging force. On used SH220LC-6 models, this circuit is particularly vulnerable to degradation due to heat exposure, vibration, and connector corrosion common in older machines.

Common Symptoms

When Code 651 is active, operators typically experience:

• Reduced hydraulic power across all functions, with noticeably slower cycle times
• Erratic pump response or inconsistent hydraulic pressure during operation
• Warning light illumination on the instrument panel (amber or red depending on severity)
• Engine over-revving or unusual RPM fluctuations under load due to improper pump control
• Complete loss of hydraulic function in severe cases where the solenoid fails entirely

Potential Causes

The most common technical causes for Code 651 on used SH220LC-6 excavators include:

• Faulty pump control solenoid valve due to internal coil failure or contamination
• Damaged wiring harness between the ECM and pump solenoid, especially at flex points near the engine mount
• Corroded or loose electrical connectors at the solenoid or ECM (common in machines with 5,000+ hours)
• Short circuit or open circuit in the solenoid control wiring
• ECM internal failure affecting the pump control output driver (rare but possible in high-hour machines)
• Low voltage supply from aging batteries or poor ground connections

How to Troubleshoot and Fix Code 651

Step 1: Visual Inspection Begin by inspecting the pump solenoid connector located on the main hydraulic pump. Check for corrosion, moisture intrusion, or damaged pins—common issues on used excavators. Examine the entire wiring harness from the ECM to the pump for chafing, particularly where it passes over the engine or frame rails.

Step 2: Electrical Testing Using a digital multimeter, measure resistance across the solenoid coil terminals (typically 3-8 ohms for this model). Check for supply voltage at the connector with the ignition on (should read approximately 12V). Test for continuity in the harness and verify proper ground connections.

Step 3: Solenoid Function Test With the engine off, disconnect the solenoid and apply direct 12V power briefly to test mechanical operation—you should hear an audible click. If the solenoid doesn't respond, replacement is necessary. For used machines, always clean connector terminals with electrical contact cleaner before reassembly.

Step 4: Advanced Diagnostics Use Sumitomo diagnostic software or compatible scan tools to monitor live solenoid current draw (typically 0.5-1.5 amps). Abnormal readings indicate internal coil issues. Clear codes after repairs and perform a functional test under load.

Disclaimer: This guide provides general troubleshooting information. Always consult the Sumitomo service manual for your specific serial number and seek professional assistance for complex electrical diagnostics or repairs.