What is Komatsu PC110-7 Fault Code H-15?

Fault Code H-15 on the Komatsu PC110-7 indicates a hydraulic oil temperature sensor circuit malfunction or abnormally high hydraulic oil temperature. This code triggers when the Engine Control Module (ECM) detects either an electrical fault in the temperature sensor circuit or when hydraulic oil exceeds the manufacturer's safe operating threshold (typically above 110°C/230°F).

This diagnostic trouble code is critical for the PC110-7's longevity because excessive hydraulic temperatures accelerate seal degradation, reduce oil viscosity, and can cause catastrophic pump failure. The temperature sensor itself is located in the hydraulic tank and sends voltage signals to the ECM to regulate fan speed and alert operators before damage occurs. On used excavators, this code often appears due to sensor degradation rather than actual overheating, though both scenarios require immediate attention.

Common Symptoms

• Warning light illuminated on the instrument cluster (hydraulic oil temperature icon)
• Noticeable decrease in hydraulic system responsiveness or cycle times
• Cooling fan running continuously at maximum speed even during light operation
• Intermittent code activation that clears after machine cool-down periods
• Unusual whining or cavitation sounds from the hydraulic pump during operation

Potential Causes

The most common causes for H-15 on used PC110-7 excavators include:

• Temperature sensor failure due to internal element degradation (common after 5,000+ operating hours)
• Corroded or damaged wiring connectors at the sensor harness connection point
• Chafed wiring along the frame rail where the harness runs near moving components
• Genuine hydraulic overheating from clogged oil coolers, low oil levels, or failing relief valves
• ECM internal fault (rare, but documented in machines with 8,000+ hours)
• Contaminated hydraulic oil reducing heat dissipation efficiency

How to Troubleshoot and Fix Code H-15

Step 1: Initial Visual Inspection Check hydraulic oil level and condition first. Inspect the temperature sensor connector (located on the hydraulic tank) for corrosion, bent pins, or oil contamination. On used excavators, this connector frequently accumulates moisture. Clean with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing Using a digital multimeter, test sensor resistance. Disconnect the sensor and measure resistance across terminals—specification is typically 200-400 ohms at 20°C (consult service manual). Test harness continuity from sensor connector to ECM pin locations. Check for shorts to ground (should read infinite resistance).

Step 3: Functional Testing Connect Komatsu diagnostic software (KOMTRAX or compatible scanner) to verify real-time temperature readings. Compare sensor output against an infrared thermometer reading of actual tank temperature. A variance greater than 10°C confirms sensor replacement needed.

Step 4: System Verification If sensor tests normal, inspect the hydraulic oil cooler for blockages, verify cooling fan operation, and check hydraulic system relief valve settings. Replace hydraulic oil and filter if contaminated or aged beyond 2,000-hour service interval.

Disclaimer: This guide provides general troubleshooting steps. Always consult the official Komatsu service manual for your specific machine serial number and seek professional diagnostic assistance for complex electrical or hydraulic system repairs.