Sumitomo SH300-6 Fault Code 380: Complete Diagnostic Guide

What is Sumitomo SH300-6 Fault Code 380?

Fault Code 380 on the Sumitomo SH300-6 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal temperature reading exceeding safe operating parameters. This code is triggered when the Electronic Control Module (ECM) detects either a voltage irregularity in the coolant temperature sensor wiring or a temperature reading that falls outside the acceptable range (typically above 105°C/221°F or below -40°C/-40°F).

This fault is critical for the SH300-6 because the coolant temperature sensor directly influences fuel injection timing, engine protection protocols, and hydraulic oil temperature management. When this code activates, the ECM may initiate engine derate or emergency shutdown to prevent catastrophic overheating damage to the engine block and head gasket.

Common Symptoms

When Code 380 is active on your SH300-6, operators typically experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Reduced engine power or derate mode limiting RPM to 1200-1500 range
• Erratic temperature gauge readings that fluctuate wildly or remain at maximum/minimum positions
• Hard starting conditions, especially during cold weather operation
• Increased white smoke from the exhaust during warm-up due to improper fuel mapping

Potential Causes

The most common technical causes for Code 380 on used SH300-6 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Wiring harness damage at the sensor connector or along the engine valley where harness rubs against the valve cover
• Corroded or loose electrical connections at the sensor plug or ECM connector pins
• ECM voltage supply issues providing incorrect reference voltage to the sensor circuit
• Actual engine overheating caused by radiator blockage, failed thermostat, or water pump malfunction
• Contaminated coolant causing sensor element coating and false readings

How to Troubleshoot and Fix Code 380

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location (typically on the thermostat housing). Check for coolant leaks, corrosion on the connector, or physical damage. On used excavators, carefully examine the wiring harness for chafing points where it contacts the engine block—this is a known wear point on the SH300-6.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms. Test the harness for continuity between the sensor connector and ECM pin terminals. Check for voltage supply (typically 5V reference) from the ECM with the ignition on.

Step 3: Component Replacement and Verification If sensor resistance is out of specification or harness shows open/short circuits, replace the faulty component. For used machines, always apply dielectric grease to connectors to prevent future corrosion. After repairs, clear codes using Sumitomo diagnostic software or compatible scan tool and perform a heat cycle test to verify proper operation.

Disclaimer: This guide provides general troubleshooting information. Always consult the Sumitomo SH300-6 service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with high-voltage systems.