Komatsu PC160LC-7 Fault Code H-6: Complete Diagnostic Guide

What is Komatsu PC160LC-7 Fault Code H-6?

Fault Code H-6 on the Komatsu PC160LC-7 indicates a hydraulic oil temperature sensor malfunction or abnormally high hydraulic oil temperature exceeding safe operating limits (typically above 110°C/230°F).

This code triggers when the hydraulic oil temperature sensor either detects excessive heat in the hydraulic system or when the sensor circuit itself experiences electrical faults. The hydraulic temperature monitoring system is critical for the PC160LC-7's performance because overheated hydraulic oil loses viscosity, reduces lubrication efficiency, accelerates component wear, and can damage expensive hydraulic pumps, motors, and control valves. The Electronic Control Module (ECM) continuously monitors this sensor to protect the excavator's hydraulic system from thermal damage.

For used excavators, this code frequently appears due to sensor degradation, wiring issues, or actual hydraulic system problems that develop over thousands of operating hours.

Common Symptoms

• Hydraulic system warning light illuminated on the instrument cluster
• Reduced hydraulic responsiveness or sluggish boom/arm/bucket movements
• Audible cooling fan running continuously at high speed
• Performance derate mode where machine automatically limits engine RPM to prevent further damage
• Visible oil discoloration (darkening or burning smell) when checking hydraulic reservoir

Potential Causes

Sensor-Related Issues:

• Failed or degraded hydraulic oil temperature sensor (common after 5,000+ hours)
• Corroded or damaged sensor connector pins due to moisture intrusion
• Broken or frayed sensor wiring harness, especially near routing points along the hydraulic tank

Actual Hydraulic System Problems:

• Clogged or restricted hydraulic oil cooler reducing heat dissipation
• Low hydraulic oil level causing inadequate cooling capacity
• Contaminated hydraulic oil filter creating excessive system pressure and heat
• Worn hydraulic pump generating excessive friction and heat
• Malfunctioning cooling fan motor or thermostat valve

How to Troubleshoot and Fix Code H-6

Step 1: Initial Visual Inspection Check the hydraulic oil level at the sight glass when the machine is cool. Inspect the hydraulic oil cooler fins for debris, dirt buildup, or damage. On used excavators, cooler blockage is extremely common and often the simplest fix.

Step 2: Test the Temperature Sensor Locate the hydraulic oil temperature sensor on the hydraulic tank (typically on the left side near the return filter). Disconnect the sensor connector and use a digital multimeter to measure resistance. At room temperature (20°C/68°F), resistance should read approximately 2,200-2,800 ohms. Compare readings against Komatsu's specifications for your specific serial number. Check for corrosion on connector terminals—a frequent issue on machines operating in wet or coastal environments.

Step 3: Inspect Wiring Harness Trace the sensor wiring harness from the sensor to the ECM connection point. Look for abraded insulation, broken wires, or pinch points where the harness contacts the frame. On the PC160LC-7, common wear areas include routing near the swing motor and along the carbody frame rails.

Step 4: Monitor Actual Oil Temperature Using Komatsu diagnostic software (KOMTRAX or equivalent), monitor real-time hydraulic oil temperature while operating. If temperature genuinely exceeds 105-110°C, investigate hydraulic system cooling capacity: clean/replace the oil cooler, verify cooling fan operation, check thermostat function, and test hydraulic pump efficiency.

Step 5: Clear Code and Test After repairs, clear the fault code using diagnostic software or by disconnecting the battery negative terminal for 30 seconds. Operate the machine under load and monitor for code reoccurrence.

Professional Tip for Used Excavators: Before replacing the temperature sensor, always verify actual oil temperature with an infrared thermometer pointed at the hydraulic tank. Many H-6 codes on older machines result from faulty sensors rather than genuine overheating, saving unnecessary diagnostic time.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC160LC-7 service manual and consider professional diagnostic assistance for complex hydraulic system issues. Improper repairs may void warranties or cause safety hazards.