What is Komatsu PC210-7 Fault Code E318?

Fault Code E318 on the Komatsu PC210-7 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal engine coolant temperature reading. This diagnostic trouble code (DTC) is generated when the Engine Control Module (ECM) detects voltage values outside the expected range from the coolant temperature sensor, or when the sensor signal suggests the engine is operating beyond safe thermal parameters.

This code is critical for the PC210-7's SAA6D107E-1 engine because accurate coolant temperature monitoring directly affects fuel injection timing, engine protection protocols, and overall performance efficiency. When the ECM cannot reliably read coolant temperature, it may force the machine into derate mode to prevent potential engine damage from overheating or operate with suboptimal fuel maps that reduce power and increase consumption.

Common Symptoms

When Code E318 is active on your Komatsu PC210-7, operators typically experience:

• Check engine light or warning lamp illuminated on the monitor panel
• Engine derate or reduced power output as the ECM enters protective mode
• Difficulty starting or extended cranking times, especially in cold conditions
• Erratic temperature gauge readings that fluctuate unexpectedly or read abnormally high/low
• Excessive black smoke from the exhaust due to improper fuel-air mixture calibration

Potential Causes

The most common technical causes for E318 on used PC210-7 excavators include:

• Failed coolant temperature sensor (resistance drift or internal circuit failure)
• Damaged wiring harness or corroded connections between the sensor and ECM, particularly at the engine-mounted connector near the thermostat housing
• Harness chafing at known rub points where the sensor wire contacts the engine block or routing brackets
• Corroded or loose ground connections affecting the sensor's reference voltage
• ECM internal fault (less common but possible in high-hour used machines)
• Low coolant level causing air pockets near the sensor probe, creating false readings

How to Troubleshoot and Fix Code E318

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the cylinder head near the thermostat housing. Check the connector for corrosion, moisture intrusion, or bent pins. On used excavators, examine the entire wiring harness for signs of abrasion, particularly where it contacts metal surfaces or passes through grommets. Verify coolant level is adequate and the system is properly bled.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At room temperature (20°C/68°F), the sensor should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity from the sensor connector to the ECM. Check for proper reference voltage (typically 5 volts) at the sensor connector with the key on, engine off.

Step 3: Advanced Diagnostics Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to read live sensor data and compare actual coolant temperature with sensor voltage output. If values are erratic or fixed at implausible readings despite temperature changes, replace the sensor. Before replacing the ECM, ensure all grounds are clean and tight, and consider testing with a known-good sensor to rule out harness issues common in used machinery.

Disclaimer: This guide provides general troubleshooting information. For used excavators with complex electrical issues or if you're unfamiliar with high-voltage systems, consult a certified Komatsu technician or qualified heavy equipment mechanic to prevent misdiagnosis or safety hazards.