Komatsu PC200-7 Fault Code H-6: Complete Diagnostic Guide

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

Fault Code H-6 indicates a malfunction in the hydraulic oil temperature sensor circuit on the Komatsu PC200-7 excavator. This code triggers when the Electronic Control Module (ECM) detects an abnormal signal from the hydraulic oil temperature sensor, typically due to an open circuit, short circuit, or sensor failure.

The hydraulic oil temperature sensor plays a critical role in protecting the PC200-7's hydraulic system. It monitors the hydraulic fluid temperature and sends real-time data to the ECM, which adjusts pump output and warns the operator when temperatures exceed safe operating limits. On older used machines, this sensor becomes prone to failure due to constant exposure to heat, vibration, and hydraulic fluid contamination. Ignoring this code can lead to hydraulic system damage, reduced component life, and costly repairs.

Common Symptoms

• Warning lamp illumination on the instrument panel (typically a hydraulic oil temperature warning light)
• Sluggish hydraulic response or reduced cycle times during operation
• Audible alarm from the cab when hydraulic temperatures rise above threshold
• Intermittent or continuous fault code display on the monitor panel
• In severe cases, the machine may enter derate mode, limiting hydraulic pump flow to prevent overheating

Potential Causes

• Failed hydraulic oil temperature sensor due to internal element degradation (common in machines with 5,000+ hours)
• Damaged wiring harness from chafing against the swing frame or hydraulic tank mounting brackets
• Corroded or loose connectors at the sensor or ECM connection points
• Short circuit to ground caused by worn insulation near heat sources or sharp edges
• ECM failure (rare but possible in high-hour used excavators exposed to moisture intrusion)
• Contaminated hydraulic fluid causing sensor element coating and false readings

How to Troubleshoot and Fix Code H-6

Step 1: Visual Inspection Start by locating the hydraulic oil temperature sensor on the hydraulic tank (typically mounted on the side or top). Inspect the sensor connector for corrosion, bent pins, or oil contamination. On used PC200-7s, check the wiring harness routing for signs of rubbing, particularly where it passes near the swing bearing or tank mounting points.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2.0-3.0 kΩ (check your service manual for exact specifications). If readings show infinite resistance (open circuit) or zero resistance (short circuit), replace the sensor.

Step 3: Circuit Verification Check voltage at the ECM connector (sensor signal wire) with the ignition on, engine off. You should see approximately 5 volts reference voltage. If voltage is absent, inspect wiring between the sensor and ECM for breaks or shorts. Use Komatsu diagnostic software (KOMTRAX or equivalent dealer tool) to monitor live sensor data and verify the ECM is receiving signals.

Step 4: Harness and Ground Inspection For used excavators, pay special attention to ground connections at the hydraulic tank and chassis. Clean all ground points with a wire brush, apply dielectric grease, and ensure tight connections. Inspect the entire harness length, securing any loose sections away from moving components.

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 if you're unfamiliar with hydraulic systems.