Sumitomo SH260LC-6 Fault Code 335: Complete Diagnostic Guide

What is Sumitomo SH260LC-6 Fault Code 335?

Fault Code 335 on the Sumitomo SH260LC-6 excavator indicates a Main Relief Valve Solenoid Circuit Malfunction, specifically related to the hydraulic system's pressure control circuit. This code triggers when the Electronic Control Module (ECM) detects an abnormal voltage, current draw, or open/short circuit condition in the main relief valve solenoid wiring or the solenoid itself.

This fault is critical for the SH260LC-6 because the main relief valve regulates maximum system pressure across all hydraulic functions. When this circuit malfunctions, the excavator cannot properly modulate hydraulic pressure, potentially leading to reduced digging force, erratic boom/arm movements, or complete hydraulic system derate to protect components from over-pressurization or cavitation damage.

Common Symptoms

When Code 335 is active on your SH260LC-6, operators typically experience:

• Hydraulic system derate or reduced power across all functions (boom, arm, bucket, and swing)
• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Erratic hydraulic response with inconsistent pressure delivery during combined operations
• Engine RPM limitation as the ECM enters protective mode to prevent hydraulic damage
• Intermittent loss of digging force, particularly noticeable during high-demand tasks like trenching or loading

Potential Causes

The most common technical causes for Code 335 on used SH260LC-6 excavators include:

• Worn or damaged solenoid coil in the main relief valve assembly (resistance outside 10-15 ohm specification range)
• Corroded or loose connector pins at the solenoid harness connection point near the main control valve
• Chafed wiring harness where the hydraulic pump lines contact the solenoid wire bundle (common rub point on this model)
• Failed ECM driver circuit unable to properly energize the solenoid (less common but documented in high-hour machines)
• Contaminated hydraulic oil causing internal valve sticking, which increases solenoid current draw beyond acceptable limits
• Voltage supply issues from corroded ground connections on the main valve body mounting surface

How to Troubleshoot and Fix Code 335

Step 1: Visual Inspection and Connector Check Begin by accessing the main control valve located beneath the operator's cab. Disconnect the solenoid connector and inspect for corrosion, bent pins, or moisture intrusion. On used excavators, this connection point frequently accumulates dirt and hydraulic mist. Clean with electrical contact cleaner and check for physical damage.

Step 2: Solenoid Resistance Testing Using a digital multimeter, measure resistance across the solenoid terminals. Specification should read 10-15 ohms at 20°C. Readings below 8 ohms indicate internal short; readings above 20 ohms or infinite resistance confirm open circuit failure requiring solenoid replacement.

Step 3: Wiring Harness Continuity and Voltage Check Trace the harness from the solenoid back to the ECM connector (located behind the battery box). Check for continuity on both power and ground circuits. With ignition on, verify 12V supply voltage at the solenoid connector. Inspect the known rub point where harness crosses the hydraulic pump—replace any abraded sections with protective loom.

Step 4: Hydraulic Oil Analysis If electrical tests pass, contaminated oil may cause valve sticking. Sample hydraulic fluid and check for metal particles or viscosity breakdown. Change filters and oil if contamination exceeds ISO 18/16/13 cleanliness code.

Step 5: ECM Driver Circuit Test Using Sumitomo diagnostic software (or compatible tool), perform active solenoid tests. Monitor current draw during energization—should be 0.8-1.2 amps. Excessive draw indicates mechanical binding; no draw confirms ECM failure.

---

Disclaimer: This guide provides general troubleshooting procedures for Code 335. Hydraulic system repairs involve high-pressure components and electrical diagnostics require proper training. Always consult a certified Sumitomo technician or qualified heavy equipment mechanic for complex repairs, especially on used machinery where undocumented modifications may exist.