Komatsu PC120LC-6 Fault Code E316: Technical Guide

What is Komatsu PC120LC-6 Fault Code E316?

Fault Code E316 indicates a malfunction in the engine coolant temperature sensor circuit. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the coolant temperature sensor, typically indicating an open circuit, short circuit, or out-of-range sensor reading.

The coolant temperature sensor is critical for the PC120LC-6's performance because it directly influences fuel injection timing, engine idle speed, and hydraulic system warm-up procedures. When this sensor fails, the ECM cannot properly regulate engine operating parameters, potentially causing inefficient combustion, increased emissions, and reduced hydraulic performance.

Common Symptoms

When Code E316 is active, operators typically experience:

• Engine warning light or malfunction indicator illuminated on the instrument panel
• Hard starting or extended cranking time, especially in cold conditions
• Rough idle or unstable engine RPM during warm-up phase
• Black smoke from exhaust due to improper fuel-air mixture calculations
• Reduced hydraulic response as the system remains in cold-start protection mode longer than necessary

Potential Causes

The most common technical causes for E316 on used PC120LC-6 excavators include:

• Damaged sensor wiring harness due to heat exposure near the engine block—a known wear point on this model series
• Corroded sensor connector terminals from coolant seepage or moisture infiltration
• Failed coolant temperature sensor (internal resistor degradation after extended service hours)
• Intermittent open circuit caused by wire chafing where the harness passes through the engine valley routing
• ECM internal fault (rare, but possible on high-hour machines with previous electrical system issues)

How to Troubleshoot and Fix Code E316

Step 1: Visual Inspection Inspect the coolant temperature sensor connector located on the thermostat housing. On used excavators, check for coolant residue, corrosion on pins, or damage to the connector body. Examine the wiring harness for abrasion points where it contacts engine components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 20°C (68°F), resistance should be approximately 2,500 ohms; at 80°C (176°F), approximately 300 ohms. Compare readings to Komatsu specifications. Test harness continuity from sensor connector to ECM pins C-23 and C-24.

Step 3: Circuit Voltage Check With ignition on and sensor disconnected, measure reference voltage at the harness connector—should read approximately 5 volts. If absent, trace wiring for breaks or check ECM power supply circuits.

Step 4: Component Replacement If sensor resistance is out of specification or harness shows continuity faults, replace the defective component. For used machines, always replace connector seals and apply dielectric grease to prevent future corrosion.

Step 5: Code Clearing and Verification Use Komatsu diagnostic software (KOMTRAX or equivalent) to clear stored codes. Perform a complete heat cycle test to verify repair success.

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Disclaimer: This guide provides general diagnostic information. Complex electrical issues or persistent codes should be evaluated by qualified Komatsu-certified technicians with proper diagnostic equipment.