Komatsu PC130-6 Fault Code S-6: Complete Diagnostic Guide

What is Komatsu PC130-6 Fault Code S-6?

Fault Code S-6 on the Komatsu PC130-6 indicates a malfunction in the hydraulic oil temperature sensor circuit. This code triggers when the Electronic Control Unit (ECU) detects abnormal voltage readings from the temperature sensor monitoring hydraulic oil heat levels.

The hydraulic oil temperature sensor is critical for the PC130-6's performance management system. It monitors oil temperature to prevent overheating damage to hydraulic pumps, motors, and seals. When this sensor fails or sends incorrect signals, the machine may enter protective derate mode, limiting operational capability to prevent catastrophic hydraulic system damage.

Common Symptoms

When Code S-6 activates on your PC130-6, operators typically experience:

• Warning lamp illumination on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic response or slower cycle times as the system enters protective mode
• Intermittent power loss during operation, especially under heavy loads
• Inaccurate temperature gauge readings showing erratic or frozen temperature displays
• Machine shutdown in severe cases when the ECU cannot verify safe operating temperatures

Potential Causes

The S-6 code on used PC130-6 excavators commonly stems from:

• Corroded or damaged sensor connector pins – particularly common where the wiring harness passes near the hydraulic tank, exposed to oil mist and moisture
• Failed hydraulic oil temperature sensor due to age-related internal resistance drift or seal deterioration
• Broken or chafed wiring at known rub points near the swing bearing or along the main boom base
• Poor ground connection at the sensor mounting location caused by rust or paint contamination
• ECU voltage supply issues from aging power harness connections or corroded ECU pins

How to Troubleshoot and Fix Code S-6

Step 1: Visual Inspection Begin with a thorough inspection of the sensor connector located near the hydraulic oil tank. On used excavators, check for oil contamination, corroded pins, or cracked connector housings. Clean all connections with electrical contact cleaner and inspect the wiring harness for visible damage, especially where it routes near moving components.

Step 2: Resistance Testing Disconnect the sensor and measure resistance across its terminals using a digital multimeter. At normal ambient temperature (20°C/68°F), resistance should read approximately 2.4-2.8 kΩ. Compare readings against Komatsu specifications for your operating temperature. Out-of-range values indicate sensor replacement is necessary.

Step 3: Circuit Voltage Check With the sensor disconnected and ignition on, measure voltage at the ECU-side connector. You should see approximately 5 volts supply voltage. No voltage indicates wiring breaks or ECU issues requiring Komatsu diagnostic software (KOMTRAX) for deeper analysis.

Step 4: Ground Verification Check continuity between the sensor ground wire and chassis ground. On used machines, remove the sensor mounting bolt, clean all mating surfaces to bare metal, and apply dielectric grease before reinstallation to prevent future corrosion.

Disclaimer: This guide provides general diagnostic procedures. For complex electrical issues or if basic troubleshooting doesn't resolve the fault, consult a certified Komatsu technician or authorized service center with proper diagnostic equipment.