What is Komatsu PC220-7 Fault Code E318?

Komatsu PC220-7 Fault Code E318 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or open/short circuit in the ECM (Engine Control Module) monitoring system. This code triggers when the ECM receives voltage readings outside the expected range (typically 0.2-4.8V) from the coolant temperature sensor, which is critical for proper fuel injection timing, engine protection, and hydraulic oil temperature regulation.

For the PC220-7's SAA6D102E-2 engine, this sensor plays a vital role in cold-start enrichment, fan clutch engagement, and preventing thermal overload during heavy digging cycles. Ignoring this code can lead to incorrect fuel mapping, reduced hydraulic efficiency, and potential engine damage from overheating.

Common Symptoms

• Engine warning lamp illuminated on the monitor panel with E318 displayed
• Hard starting when the engine is cold, or excessive white smoke during warm-up
• Cooling fan runs continuously at high speed regardless of actual engine temperature
• Reduced hydraulic power or sluggish arm/bucket response due to ECM entering derate mode
• Inaccurate temperature gauge readings showing no change or stuck at cold/hot positions

Potential Causes

The E318 code on used PC220-7 excavators typically stems from age-related deterioration:

• Coolant temperature sensor failure – Internal thermistor degradation common after 6,000+ operating hours
• Corroded or loose connector at the sensor (located on the thermostat housing near cylinder head)
• Damaged wiring harness between sensor and ECM, particularly where the harness runs along the engine block and experiences heat cycling
• Coolant contamination causing sensor element coating or corrosion
• ECM internal circuit failure (rare, but possible on machines with 10+ years of service)
• Poor ground connection at engine block grounding points G101 or G102

How to Troubleshoot and Fix Code E318

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor connector for corrosion, bent pins, or moisture intrusion. On used excavators, check the wiring harness routing for signs of chafing against engine components or heat damage near the exhaust manifold. Clean connectors with electrical contact cleaner and dielectric grease.

Step 2: Sensor Resistance Testing Disconnect the sensor (2-pin connector) and measure resistance across the sensor terminals using a digital multimeter. At 20°C (68°F), resistance should read approximately 2.3-2.7 kΩ; at 80°C (176°F), it should drop to 0.3-0.4 kΩ. Values outside this range indicate sensor replacement is needed (Komatsu part #6732-81-3140).

Step 3: Circuit Voltage Check With ignition ON and sensor disconnected, measure voltage at the harness connector. You should see approximately 5V reference voltage on the signal wire. If voltage is absent or reads battery voltage (24V), trace the harness for shorts or open circuits back to ECM connector E2-14.

Step 4: ECM Data Verification Using Komatsu diagnostic software (KOMTRAX or PC Service Tool), monitor live coolant temperature data. Compare displayed temperature against actual engine temp (infrared thermometer). A significant variance confirms sensor/circuit fault rather than ECM issues.

For used excavators with over 8,000 hours, always inspect connector seals and harness grommets for age-related cracking before parts replacement—many E318 codes resolve with proper connector service and harness rerouting away from heat sources.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC220-7 service manual and consider professional diagnostic assistance for complex electrical issues or warranty considerations.