Sumitomo SH240-5 Fault Code 335: Complete Diagnostic Guide

What is Sumitomo SH240-5 Fault Code 335?

Fault Code 335 on the Sumitomo SH240-5 excavator indicates a Throttle Position Sensor (TPS) Circuit Malfunction or abnormal voltage signal detected by the Engine Control Module (ECM). This code specifically points to an electrical issue within the throttle position sensor circuit, which can involve the sensor itself, wiring harness, or ECM communication failure.

The throttle position sensor is critical for the SH240-5's engine management system, as it communicates accelerator pedal position to the ECM to regulate fuel delivery and engine speed. When this circuit fails, the excavator's performance and fuel efficiency are directly compromised, potentially leading to engine protection modes that limit productivity on job sites.

Common Symptoms

When Code 335 is active on your SH240-5, operators typically experience:

• Engine warning light illuminated on the instrument cluster with possible audible alarm
• Erratic engine RPM response or delayed throttle reaction when operating controls
• Engine stuck at idle or low RPM regardless of throttle input position
• Derate mode activation, limiting engine power output to protect components
• Intermittent loss of throttle control, particularly during temperature changes or machine vibration

Potential Causes

The most common technical causes for Code 335 on used SH240-5 excavators include:

• Throttle position sensor internal failure due to carbon buildup or worn potentiometer contacts (common after 6,000+ operating hours)
• Damaged wiring harness near the engine firewall where cables experience rubbing against frame components
• Corroded or loose connector pins at the TPS connector or ECM harness connections
• Poor ground connection at the sensor mounting point or chassis ground strap deterioration
• ECM voltage supply issues providing incorrect reference voltage (typically should be 5V ± 0.25V)
• Water intrusion into the TPS connector from worn cab floor seals (common problem area on older SH240-5 models)

How to Troubleshoot and Fix Code 335

Step 1: Visual Inspection and Connection Check Begin by inspecting the throttle position sensor located on the fuel injection pump or throttle body assembly. Check for physical damage, oil contamination, or corrosion on the connector terminals. Clean connections with electrical contact cleaner and ensure the locking tab is fully engaged.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, backprobe the TPS connector with the key on, engine off. Verify the reference voltage reads approximately 5V DC. Check the signal wire voltage while slowly moving the throttle—it should sweep smoothly from approximately 0.5V (idle) to 4.5V (full throttle). Any erratic readings or dead spots indicate sensor replacement is needed.

Step 3: Wiring Harness Continuity Test Disconnect both the TPS connector and ECM harness connector. Test continuity between corresponding pins and check for shorts to ground. On used excavators, pay special attention to harness routing near the engine mount brackets and hydraulic lines where friction wear commonly occurs on the SH240-5 chassis.

Step 4: Ground Circuit Verification Verify the sensor ground circuit has less than 0.5 ohms resistance to chassis ground. Clean and tighten the engine ground strap connections, as corrosion here frequently causes intermittent sensor faults on older machines.

Step 5: Component Replacement If testing confirms sensor failure, replace the throttle position sensor with OEM or quality aftermarket parts. After installation, clear codes using Sumitomo diagnostic software or compatible scan tool and perform throttle calibration procedures per manufacturer specifications.

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Disclaimer: This guide provides general troubleshooting information. Always consult the Sumitomo SH240-5 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional system damage.