What is Komatsu PC210LC-7 Fault Code E318?

Fault Code E318 on the Komatsu PC210LC-7 indicates a malfunction in the Engine Coolant Temperature (ECT) sensor circuit, specifically detecting an abnormally high voltage signal or open circuit condition. This diagnostic trouble code (DTC) is generated when the engine control module (ECM) receives voltage readings outside the normal operating range from the ECT sensor, typically above 4.8 volts when the system expects 0.5-4.5 volts depending on coolant temperature.

The ECT sensor plays a critical role in the PC210LC-7's performance management system. It directly influences fuel injection timing, idle speed control, and engine protection protocols. When this sensor circuit fails, the ECM cannot accurately determine engine temperature, potentially leading to improper fuel mapping, excessive emissions, and inadequate overheating protection on this 6-cylinder SAA6D107E-1 engine.

Common Symptoms

When Code E318 is active on your Komatsu PC210LC-7, operators typically experience:

• Engine warning light illuminated on the monitor panel (amber or red depending on severity)
• Hard starting conditions, especially when the engine is cold, due to incorrect fuel enrichment
• Rough idle or hunting RPM as the ECM defaults to predetermined temperature values
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Reduced engine power or derate mode activation as a protective measure during extended fault conditions

Potential Causes

The most common technical failures triggering E318 on used PC210LC-7 excavators include:

• Open circuit in ECT sensor wiring harness caused by wire breakage near movement points (especially where the harness routes over the engine block near the thermostat housing)
• Corroded or loose connector pins at the ECT sensor plug—a frequent issue on machines with 8,000+ operating hours exposed to moisture
• Failed ECT sensor with internal open circuit (the sensor itself contains a thermistor that can fail)
• Damaged ECM connector terminals at pin locations corresponding to the coolant temperature circuit
• Shorted sensor ground wire due to harness chafing against the engine block or frame

How to Troubleshoot and Fix Code E318

Step 1: Visual Inspection Begin by locating the ECT sensor on the engine block (typically near the thermostat housing on the SAA6D107E-1 engine). Inspect the sensor connector for corrosion, bent pins, moisture intrusion, or physical damage. On used excavators, check the entire wiring harness route for signs of rubbing, especially where it contacts metal surfaces or moving components.

Step 2: Electrical Testing Disconnect the ECT sensor connector. Using a digital multimeter, measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,400-2,700 ohms. If the reading shows infinite resistance (open circuit) or zero ohms (short circuit), replace the sensor. Next, check for supply voltage at the harness connector with the ignition on—you should see approximately 5 volts from the ECM.

Step 3: Harness Continuity Check With the sensor disconnected and ignition off, test continuity between the ECM connector (consult the PC210LC-7 wiring diagram for specific pin locations) and the sensor harness plug. Check both the signal wire and ground return path. Resistance should be less than 1 ohm. Any reading above 5 ohms indicates corroded connections or damaged wiring requiring repair or replacement.

Step 4: Advanced Diagnosis If sensor and wiring tests pass, connect Komatsu KOMTRAX diagnostic software or a compatible scan tool to monitor live ECT voltage data. Observe whether voltage readings fluctuate abnormally or remain fixed at maximum voltage (typically 5V for open circuit). For used machines with previous repair history, verify no aftermarket harness splices have been made improperly, as these create high-resistance points.

Disclaimer: While this guide provides technical troubleshooting steps, complex electrical diagnostics on heavy equipment should be performed by qualified technicians with proper diagnostic tools. Always consult the official Komatsu PC210LC-7 service manual and follow lockout/tagout procedures before performing any electrical work.