Sumitomo SH290-5 Fault Code 335: Complete Diagnostic Guide

What is Sumitomo SH290-5 Fault Code 335?

Fault Code 335 on the Sumitomo SH290-5 excavator indicates a malfunction in the Engine Speed Sensor Circuit or an abnormal signal from the crankshaft position sensor.

This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an irregular or missing signal from the engine speed sensor during operation. The sensor monitors crankshaft rotation and provides critical data for fuel injection timing, engine speed control, and overall performance monitoring. On used Sumitomo excavators, this code is particularly important because the engine speed sensor directly affects fuel delivery precision, idle stability, and the machine's ability to respond to load changes during heavy digging or lifting operations.

Common Symptoms

When Code 335 is active on your SH290-5, operators typically experience:

• Erratic engine idle or unexpected RPM fluctuations during normal operation
• Hard starting or extended cranking time, especially when the engine is cold
• Loss of power under load, with the engine struggling to maintain consistent RPM
• Engine stalling during idle or low-speed operation
• Check Engine light illuminated on the instrument panel with possible audible warning alarm

Potential Causes

The most common technical causes for Code 335 on used SH290-5 excavators include:

• Damaged or contaminated engine speed sensor due to oil leaks, metal debris, or heat exposure
• Corroded or loose wiring connectors at the sensor harness connection point
• Broken or frayed wiring in the sensor harness, particularly where it routes near the engine block or vibration-prone areas
• Worn sensor reluctor wheel (tone ring) on the crankshaft with missing teeth or debris buildup
• ECM internal fault or poor ground connections affecting signal processing
• Sensor air gap issues caused by improper installation or mounting bracket damage

How to Troubleshoot and Fix Code 335

Step 1: Visual Inspection Begin by locating the engine speed sensor on the SH290-5's engine block (typically near the flywheel housing). Inspect the sensor body for physical damage, oil contamination, or metal shavings. Check the wiring harness for visible wear, especially at flex points where the harness may rub against the engine or frame.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. Typical readings should be between 150-300 ohms (consult service manual for exact specifications). Test the harness continuity from sensor connector to ECM, checking for opens or shorts to ground. Inspect connector pins for corrosion or bent terminals—common issues in used machines exposed to moisture.

Step 3: Signal and Air Gap Verification Check the sensor air gap between the sensor tip and reluctor wheel (typically 0.5-1.5mm). Use a feeler gauge to verify proper clearance. If equipped with diagnostic software, monitor the live sensor signal during cranking to confirm proper AC voltage generation (typically 0.5-5V AC when cranking).

Step 4: Component Replacement If testing confirms sensor failure, replace the engine speed sensor with OEM or quality aftermarket parts. For used excavators, always apply dielectric grease to connectors and secure harnesses away from heat sources and moving components to prevent premature failure.

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Disclaimer: This guide provides general troubleshooting information for Code 335. Always consult the official Sumitomo service manual for your specific machine serial number and consult qualified diesel technicians for complex electrical diagnostics or repairs involving the ECM system.