Komatsu PC200-7 Fault Code E-6: Complete Technical Guide

What is Komatsu PC200-7 Fault Code E-6?

Fault Code E-6 on the Komatsu PC200-7 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an overheating condition detected by the Engine Control Module (ECM). This code specifically relates to abnormal voltage readings from the water temperature sensor located in the engine's cooling system, or an actual high-temperature event that triggers protective engine derating.

The coolant temperature sensor provides critical data to the ECM to regulate fuel injection timing, engine warm-up cycles, and hydraulic oil temperature management. On the PC200-7's SAA6D102E-2 engine, this sensor directly impacts performance and longevity. Ignoring this code can lead to severe engine damage, cracked cylinder heads, or complete thermal shutdown during operation.

Common Symptoms

When Code E-6 is active, operators typically experience:

• Warning lamp illumination on the monitor panel, often accompanied by an audible alarm
• Engine power reduction (derating) as the ECM enters limp mode to prevent overheating damage
• Erratic temperature gauge readings or gauge pegged at maximum despite normal operating conditions
• Delayed hydraulic response due to ECM compensating for perceived temperature abnormalities
• Black smoke from exhaust if the ECM defaults to rich fuel mixture settings in failsafe mode

Potential Causes

The most common technical failures triggering E-6 on used PC200-7 machines include:

• Faulty coolant temperature sensor (common failure point after 8,000+ operating hours)
• Corroded or loose connector pins at the sensor harness (three-wire connector prone to moisture intrusion)
• Damaged wiring harness particularly where it routes near the exhaust manifold or rubs against engine mount brackets
• Low coolant level or air pockets in the cooling system causing genuine overheating events
• Failed thermostat stuck closed, creating actual high-temperature conditions
• ECM internal fault or corrupted temperature calibration data (less common but possible in machines with electrical system damage history)

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Before connecting diagnostic tools, inspect the coolant temperature sensor (located on the thermostat housing near the front of the cylinder head). Check the three-wire connector for corrosion, oil contamination, or pushed-back pins. On used excavators, this connector frequently suffers from coolant seepage. Clean contacts with electrical cleaner and ensure positive lock engagement.

Step 2: Sensor Circuit Testing Using a digital multimeter, backprobe the sensor connector with the ignition on, engine off. Verify 5-volt reference supply from the ECM on the signal wire. Check sensor ground continuity (should read less than 0.5 ohms to battery negative). Measure sensor resistance: at 68°F (20°C), resistance should be approximately 2,400-2,700 ohms. Values outside this range indicate sensor replacement is necessary (Komatsu part number 6732-81-3140).

Step 3: Wiring Harness Verification Trace the sensor harness from connector to ECM pins (typically a 15-20 minute task). Pay special attention to areas where the harness contacts the alternator bracket or coolant hoses—common rub-through points on machines exceeding 10,000 hours. Perform a wiggle test while monitoring live data with Komatsu diagnostic software (KOMTRAX or PC-based tools) to identify intermittent opens or shorts.

Step 4: System Functional Test After repairs, clear the code using diagnostic software. Verify actual coolant temperature with an infrared thermometer against displayed values. Temperature readings should correlate within 5°F. Test the system under load conditions to ensure the code does not return.

For used excavators, always inspect the radiator core for blockages and pressure-test the cooling system to 16 PSI—degraded radiator caps or internal leaks often contribute to genuine overheating that triggers E-6 alongside sensor issues.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC200-7 service manual and consider professional diagnostic assistance for complex electrical issues or persistent fault codes. Improper repairs may void warranties or create safety hazards.