Sany SY245/265H Fault Code 68: Complete Diagnostic Guide

What is Sany SY245/265H Fault Code 68?

Fault Code 68 on the Sany SY245/265H excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Mitsubishi Heavy Industries engine control module (ECM).

This diagnostic trouble code (DTC) specifically relates to the coolant temperature sensor (CTS) signal being outside normal operating parameters—either too high, too low, or completely absent. The Mitsubishi ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine warm-up cycles, and prevent overheating damage. When Code 68 triggers, the engine management system may enter a protective derate mode to prevent catastrophic engine failure, making immediate diagnosis critical for maintaining productivity and preventing expensive repairs.

Common Symptoms

When Fault Code 68 is active on your SY245/265H, you may experience:

• Check engine light or warning indicator illuminated on the instrument cluster
• Engine running in limp mode with reduced power output and limited RPM range
• Hard starting or extended cranking time, especially during cold weather conditions
• Engine running excessively rich or lean, causing black smoke or rough idle
• Cooling fan running continuously at high speed, regardless of actual engine temperature

Potential Causes

The most common technical reasons for Code 68 on used Sany excavators include:

• Faulty coolant temperature sensor due to internal resistance degradation (common after 5,000+ operating hours)
• Damaged wiring harness near the engine block where vibration causes wire chafing against metal surfaces
• Corroded or loose electrical connectors at the CTS plug—moisture intrusion is frequent in excavator environments
• Low coolant level causing inaccurate temperature readings or sensor exposure to air
• ECM internal fault or corrupted calibration data (less common but possible in older machines)
• Broken sensor mounting threads causing coolant leaks and sensor displacement

How to Troubleshoot and Fix Code 68

Step 1: Visual Inspection Begin by checking actual coolant level in the radiator and overflow tank. Inspect the coolant temperature sensor (typically located on the engine block near the thermostat housing) for physical damage, coolant leaks, or loose mounting. Examine the wiring harness from sensor to ECM for obvious damage, rubbing points, or burned insulation.

Step 2: Electrical Testing Disconnect the CTS connector and use a digital multimeter to measure sensor resistance. At room temperature (20°C/68°F), resistance should typically read between 2,000-3,000 ohms (consult Mitsubishi specifications). Test continuity in the wiring harness between sensor connector and ECM pins. Check for short circuits to ground by measuring resistance between signal wire and chassis ground (should read infinite/open circuit).

Step 3: Live Data Analysis Using Mitsubishi MUT-III diagnostic software or compatible scan tool, monitor live coolant temperature readings while engine warms up. Temperature should rise smoothly from ambient to approximately 82-95°C (180-203°F). Erratic readings, frozen values, or implausible temperatures confirm sensor or circuit failure.

Step 4: Component Replacement For used excavators, always inspect connector terminals for corrosion—clean with electrical contact cleaner and apply dielectric grease before reconnecting. Replace the coolant temperature sensor with genuine Mitsubishi parts to ensure ECM compatibility. After replacement, clear codes using diagnostic software and perform a test cycle to verify repair.

---

Disclaimer: This guide provides general diagnostic information. Complex electrical issues or engine problems should be evaluated by certified Mitsubishi or Sany technicians with proper diagnostic equipment. Always consult factory service manuals for model-specific procedures and specifications.