Komatsu PC750-7 Fault Code E202: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E202?

Fault Code E202 on the Komatsu PC750-7 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending irregular voltage signals or detecting temperatures outside the normal operating parameters.

The coolant temperature sensor plays a critical role in the PC750-7's SAA6D140E-5 engine management system. It provides real-time data to the ECM for fuel injection timing, engine protection protocols, and hydraulic system temperature compensation. When this sensor fails or sends erratic signals, the machine cannot properly regulate engine performance, potentially leading to overheating, reduced power output, or premature component wear.

Common Symptoms

When Code E202 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with possible audible alarm
• Reduced engine power or derate mode activation to prevent overheating damage
• Erratic temperature gauge readings that fluctuate abnormally or show implausible values
• Difficulty starting in cold conditions due to improper fuel enrichment
• Increased fuel consumption as the ECM defaults to safe-mode fuel mapping

Potential Causes

The most common technical causes for E202 on used PC750-7 excavators include:

• Faulty coolant temperature sensor (common failure point after 8,000+ operating hours)
• Damaged or corroded wiring harness at connector points, especially near the engine block where heat and vibration cause deterioration
• Loose or corroded electrical connections at the sensor plug or ECM terminals
• Coolant contamination causing sensor element degradation
• ECM internal fault (rare, but possible in high-hour machines)
• Broken or chafed wires along harness routing points where contact with engine components occurs

How to Troubleshoot and Fix Code E202

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 terminals. On used excavators, examine the entire wiring harness for rub-through points, especially where it contacts engine mounts or vibrates against metal surfaces.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance at various temperatures. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Check voltage supply from the ECM—it should provide approximately 5 volts to the sensor. Inspect harness continuity between the sensor and ECM connector.

Step 3: Component Replacement and Verification If resistance values are out of specification or the sensor shows physical deterioration, replace it with a genuine Komatsu part (part number 6732-81-3110 or equivalent). After replacement, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool. Monitor coolant temperature readings during a complete warm-up cycle to verify proper operation.

Critical for Used Equipment: Before replacing the sensor, thoroughly clean all electrical connectors with contact cleaner and apply dielectric grease to prevent future corrosion—a common issue in older machines that can mimic sensor failure.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and seek professional assistance from certified technicians for complex repairs.