What is Komatsu PC100-6 Fault Code E102?

Fault Code E102 on the Komatsu PC100-6 indicates a malfunction in the engine coolant temperature sensor circuit. This diagnostic trouble code 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 sensor degradation.

The coolant temperature sensor is critical for proper engine management on the PC100-6's diesel engine. It provides real-time data to the ECM to regulate fuel injection timing, idle speed, and fan operation. When this circuit fails, the ECM cannot accurately monitor engine temperature, potentially leading to overheating, poor fuel economy, and reduced engine protection. For used excavators, this sensor and its wiring are particularly vulnerable to corrosion and heat-related deterioration over years of operation.

Common Symptoms

• Engine warning light illuminated on the instrument panel, often accompanied by a continuous or intermittent alarm
• Engine running in derate mode or limp mode, limiting power output and hydraulic performance
• Cooling fan running continuously at high speed regardless of actual engine temperature
• Difficulty starting, especially in cold conditions, or rough idle during warm-up
• Inaccurate temperature gauge readings, showing either maximum hot or minimum cold positions

Potential Causes

The most common technical causes for E102 on used PC100-6 excavators include:

• Coolant temperature sensor failure due to internal resistance drift or element breakdown (common after 5,000+ operating hours)
• Wiring harness damage at known rub points near the engine block or behind the hydraulic pump mounting area
• Corroded or loose connector pins at the sensor plug, especially on machines operating in wet or coastal environments
• ECM pin corrosion or water intrusion in the engine controller connector
• Damaged or chafed wiring insulation where the harness passes through metal grommets or brackets

How to Troubleshoot and Fix Code E102

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the sensor connector for corrosion, bent pins, or moisture. On used excavators, check the entire wiring harness route for abrasion points, particularly where it contacts the engine or frame. Look for discolored insulation indicating heat damage.

Step 2: Electrical Testing Disconnect the sensor and use a multimeter to measure resistance across the sensor terminals. At 20°C (68°F), resistance should typically read 2-3 kΩ (consult Komatsu service manual for exact specifications). Test for continuity in the harness from sensor to ECM connector. Check for short circuits to ground by measuring resistance between each wire and chassis ground (should read infinite resistance).

Step 3: Voltage Signal Verification With ignition on and sensor disconnected, measure reference voltage at the harness connector (should be approximately 5V from ECM). If voltage is absent or incorrect, suspect ECM issues or harness damage. Reconnect sensor and use Komatsu diagnostic software to monitor live coolant temperature data while warming the engine—readings should increase smoothly without erratic jumps.

Step 4: Component Replacement If sensor resistance is out of specification or the signal remains erratic after harness repairs, replace the coolant temperature sensor with a genuine Komatsu part. For used machines, always apply dielectric grease to connector terminals before reassembly to prevent future corrosion. Clear the fault code using diagnostic software and verify proper operation through a complete heat cycle.

Disclaimer: This guide provides general technical information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnostic services for complex electrical issues.