Komatsu PC800-7 Fault Code E218: Complete Diagnostic Guide

What is Komatsu PC800-7 Fault Code E218?

Fault Code E218 on the Komatsu PC800-7 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or open/short circuit condition in the water temperature sensor system. This code is generated when the Engine Control Module (ECM) receives voltage readings outside the predetermined range (typically 0.2-4.8V) from the coolant temperature sensor.

This fault is critical for the PC800-7's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine warm-up cycles, and prevent overheating damage to the Komatsu SAA6D140E-5 engine. Ignoring this code can lead to poor fuel economy, excessive emissions, and potential engine damage.

Common Symptoms

• Engine warning light illuminated on the instrument cluster with reduced engine power output
• Engine running in "limp mode" with limited RPM (typically restricted to 1,500-1,800 RPM)
• Difficulty starting when the engine is cold, or excessive white smoke during warm-up
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Inaccurate temperature gauge readings showing extreme cold or hot conditions

Potential Causes

The most common causes of E218 on used PC800-7 excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Damaged or corroded wiring harness connections at the sensor plug (common wear point near the thermostat housing)
• Chafed wiring where the harness contacts the engine block or hydraulic lines during vibration
• Corroded ECM connector pins (particularly in machines operating in coastal or high-humidity environments)
• Faulty ECM internal circuitry (less common but possible in high-hour machines)
• Coolant contamination causing sensor element coating or failure

How to Troubleshoot and Fix Code E218

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the connector. On used excavators, examine the wiring harness for rub points, particularly where it routes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Test harness continuity from the sensor connector to the ECM connector, checking for opens or shorts to ground.

Step 3: Voltage Signal Check With the sensor connected and ignition on (engine off), backprobe the sensor connector and measure supply voltage from the ECM—it should read approximately 5V. If voltage is absent or incorrect, trace the circuit back to the ECM for wiring faults or ECM issues.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part (P/N 6732-81-3110 or equivalent). For used machines, always apply dielectric grease to connector pins to prevent future corrosion. Clear codes using Komatsu diagnostic software (KOMTRAX) and verify repair.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and seek professional assistance for complex electrical diagnostics or repairs.