Komatsu PC400-6 Fault Code H-13: Complete Diagnostic Guide

What is Komatsu PC400-6 Fault Code H-13?

Fault Code H-13 on the Komatsu PC400-6 indicates a hydraulic oil temperature sensor circuit malfunction or abnormally high hydraulic oil temperature. This code is triggered when the Electronic Control Module (ECM) detects either an electrical fault in the temperature sensor circuit or when hydraulic oil temperature exceeds the safe operating threshold (typically above 110-120°C).

This fault is critical for the PC400-6 because excessive hydraulic oil temperature can cause rapid degradation of seals, reduced hydraulic efficiency, and potential damage to the hydraulic pump and control valves. The monitoring system protects expensive hydraulic components by alerting operators before catastrophic failure occurs.

Common Symptoms

When Code H-13 is active, operators typically experience:

• Hydraulic oil temperature warning light illuminated on the instrument panel
• Reduced machine performance or automatic derate mode limiting hydraulic functions
• Audible warning alarm sounding in the cab during operation
• Sluggish hydraulic response, particularly during heavy digging or lifting operations
• Visible smoke or burning smell from the hydraulic tank area in severe overheating cases

Potential Causes

The most common technical causes for H-13 on used PC400-6 excavators include:

• Hydraulic oil temperature sensor failure due to age-related degradation or contamination
• Damaged wiring harness near the hydraulic tank, especially at known rub points where the harness contacts the frame
• Corroded or loose electrical connectors at the sensor or ECM interface
• Actual hydraulic system overheating caused by clogged oil cooler fins, failed cooling fan, or low oil level
• Faulty hydraulic oil cooler with reduced heat exchange efficiency
• ECM calibration issues or internal ECM faults (less common)

How to Troubleshoot and Fix Code H-13

Step 1: Visual Inspection Begin by inspecting the hydraulic oil temperature sensor located on the hydraulic tank. Check the wiring harness for visible damage, chafing, or oil contamination. On used excavators, pay special attention to connector pins for corrosion—clean with electrical contact cleaner if necessary.

Step 2: Sensor Circuit Testing Using a digital multimeter, measure the sensor resistance. The PC400-6 temperature sensor typically shows 200-300 ohms at 20°C (consult your service manual for exact specifications). Check for open circuits or short circuits to ground in the wiring between the sensor and ECM.

Step 3: Verify Actual Temperature Use an infrared thermometer to measure actual hydraulic oil temperature. If oil temperature is genuinely high (above 100°C), inspect the hydraulic oil cooler for blockages, verify cooling fan operation, and check hydraulic oil level and condition.

Step 4: Sensor Replacement and System Reset If electrical testing confirms sensor failure, replace with a genuine Komatsu temperature sensor (Part #: verify with dealer). After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then test operate the machine.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC400-6 service manual and consider professional technician assistance for complex electrical or hydraulic system repairs.