Sumitomo SH240-6 Fault Code 687: Complete Diagnostic Guide

What is Sumitomo SH240-6 Fault Code 687?

Fault Code 687 on the Sumitomo SH240-6 indicates a Hydraulic Oil Temperature Sensor Circuit malfunction or an abnormal temperature reading in the hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects voltage values outside the normal operating range from the hydraulic oil temperature sensor, or when hydraulic oil temperatures exceed safe operational thresholds.

This fault is critical for the SH240-6 because hydraulic oil temperature directly affects system viscosity, component lubrication, and seal integrity. The excavator's hydraulic system relies on precise temperature monitoring to prevent catastrophic damage to pumps, motors, and control valves. Ignoring this code can lead to accelerated wear, reduced hydraulic efficiency, and expensive component failures.

Common Symptoms

When Code 687 is active, operators typically experience:

• Warning light illumination on the instrument panel (hydraulic oil temperature icon or check engine light)
• Reduced hydraulic power or sluggish boom/arm/bucket movements as the system enters derate mode
• Erratic temperature gauge readings or gauge stuck at maximum/minimum positions
• Intermittent alarm buzzer activation, especially during warm-up or high-load operations
• Machine automatically limiting engine RPM to protect hydraulic components from thermal damage

Potential Causes

The most common technical reasons for Code 687 on used SH240-6 excavators include:

• Faulty hydraulic oil temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins near the hydraulic tank
• Shorted or open sensor circuit caused by wire chafing against the tank mounting bracket (known wear point on this model)
• Contaminated hydraulic oil causing actual overheating conditions that trigger legitimate high-temperature warnings
• ECM internal fault or corrupted calibration data (rare but possible in older machines)
• Poor electrical ground connection at the sensor mounting location due to rust or paint buildup

How to Troubleshoot and Fix Code 687

Step 1: Visual Inspection Begin by inspecting the hydraulic oil temperature sensor located on the hydraulic oil tank (typically on the left side near the return filter). Check for physical damage, oil leaks around the sensor body, and corroded connector terminals. On used excavators, examine the wiring harness for abrasion points where it routes along the tank edge—this is a common failure location.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At 20°C (68°F), resistance should typically read between 2,000-3,000 ohms (consult service manual for exact specifications). Next, check for voltage supply at the harness connector with ignition on—you should see approximately 5 volts from the ECM. Test for continuity between sensor ground and chassis ground.

Step 3: Live Data Analysis Connect Sumitomo diagnostic software (or compatible scan tool) to monitor real-time temperature values. Compare sensor readings against actual hydraulic oil temperature measured with an infrared thermometer. If readings differ by more than 10°C, replace the sensor. Clear the code and observe if it returns immediately or only under specific conditions.

Step 4: Component Replacement If testing confirms sensor failure, replace with an OEM or equivalent sensor ensuring proper thread sealant application. For used machines, always replace the connector pigtail if corrosion is present—repair kits are available. After installation, bleed any air from the sensor port and verify proper torque specifications (typically 15-20 ft-lbs).

Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual for your specific serial number range. If you lack proper diagnostic tools or experience with hydraulic systems, contact a certified Sumitomo technician to prevent injury or further machine damage.