Komatsu PC750-7 Fault Code H-13: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code H-13?

Fault Code H-13 on the Komatsu PC750-7 indicates a hydraulic oil temperature sensor circuit malfunction or abnormal high temperature reading in the hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects either an electrical fault in the temperature sensor circuit or when hydraulic oil temperatures exceed safe operating thresholds (typically above 110-120°C).

This fault is critical for the PC750-7 because excessive hydraulic temperatures can cause rapid degradation of seals, accelerated oil breakdown, and potential damage to hydraulic pumps and motors. The machine's monitoring system uses this sensor data to protect expensive hydraulic components and prevent catastrophic failures. When H-13 activates, the ECM may initiate protective measures including power derate or automatic shutdown sequences.

Common Symptoms

• Hydraulic temperature warning light illuminated on the operator display panel
• Reduced engine power or hydraulic flow as the system enters protective derate mode
• Audible alarm sounding in the cab when temperature thresholds are exceeded
• Sluggish hydraulic response or slower cycle times during operation
• Automatic engine shutdown in severe cases where temperatures reach critical levels

Potential Causes

The most common causes of H-13 on used PC750-7 excavators include:

• Hydraulic oil temperature sensor failure due to age-related degradation or contamination exposure
• Damaged or corroded wiring harness at sensor connector points, particularly where harnesses route near hot engine components
• Actual hydraulic system overheating caused by restricted oil cooler fins, low coolant levels, or failed cooling fan operation
• Clogged hydraulic oil filters creating excessive system backpressure and heat generation
• ECM calibration issues or software glitches causing false temperature readings
• Worn hydraulic pump generating excessive heat due to internal leakage and inefficiency

How to Troubleshoot and Fix Code H-13

Step 1: Visual Inspection Begin by checking the hydraulic oil cooler for debris blockage, bent fins, or damage. Inspect the cooling fan operation and verify proper coolant levels. On used excavators, examine the sensor wiring harness for chafing, particularly where it passes through the swing bearing area or near exhaust components.

Step 2: Sensor Circuit Testing Using a digital multimeter, disconnect the hydraulic temperature sensor connector and measure resistance across the sensor terminals. Compare readings against Komatsu specifications (typically 200-300 ohms at 20°C). Check for voltage supply at the harness connector (should read approximately 5V reference voltage). Inspect connector pins for corrosion or bent terminals—common issues in older machines.

Step 3: Live Temperature Verification Connect Komatsu diagnostic software (KOMTRAX or PC-based diagnostic tool) to monitor real-time temperature readings. Compare sensor output against an infrared thermometer reading taken directly at the hydraulic tank. A variance greater than 10°C indicates sensor replacement is needed.

Step 4: System Pressure and Flow Testing If sensor tests pass, investigate actual overheating causes. Check hydraulic oil condition for contamination or breakdown. Test system pressure and flow rates to identify worn pumps or restricted circuits causing excessive heat generation.

For used excavators specifically: Always inspect harness routing and protection before replacing sensors, as vibration-induced wire damage is extremely common on high-hour machines.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual and consider professional technician assistance for complex repairs. Improper diagnosis may lead to equipment damage or safety hazards.