What is Komatsu PC120-6 Fault Code H-13?

Fault Code H-13 on the Komatsu PC120-6 indicates a hydraulic pump pressure sensor circuit malfunction or abnormal pressure reading in the main hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects voltage signals outside the acceptable range from the main pump pressure sensor, or when actual hydraulic pressure deviates significantly from expected values during operation.

The PC120-6 relies on precise hydraulic pressure monitoring to optimize pump output and protect the system from over-pressure conditions. This fault code is critical because it can lead to reduced hydraulic performance, inefficient fuel consumption, and potential damage to expensive hydraulic components like the main pump, control valves, or relief valves if left unaddressed.

Common Symptoms

• Hydraulic system warning light illuminated on the instrument panel
• Noticeably reduced digging force or slower cylinder movement across all functions
• Erratic boom or arm response, especially under heavy loads
• Possible activation of engine derate mode limiting RPM to protect the hydraulic system
• Intermittent loss of auxiliary hydraulic functions (breaker or grapple circuits)

Potential Causes

The H-13 code typically stems from issues common in used excavators with significant operating hours:

• Faulty main pump pressure sensor due to internal component degradation or contaminated hydraulic oil infiltration
• Damaged or corroded wiring harness at sensor connector points, particularly where the harness runs along the pump housing (known rub point on PC120-6 models)
• Broken or shorted sensor signal wire between the pressure sensor and ECM
• Low hydraulic oil level or severely contaminated oil affecting actual system pressure
• Failed relief valve causing abnormal pressure spikes that trigger sensor fault detection
• ECM internal circuit failure (less common but possible on high-hour machines)

How to Troubleshoot and Fix Code H-13

Step 1: Visual Inspection Locate the main pump pressure sensor mounted on the hydraulic pump assembly. Inspect the sensor connector for corrosion, oil contamination, or bent pins. Check the wiring harness for obvious damage, particularly where it contacts metal surfaces near the pump. On used excavators, this harness frequently shows wear from vibration and heat exposure.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across sensor terminals (typically 200-400 ohms when functioning properly—consult service manual for exact specifications). Check supply voltage at the connector with ignition on (should read approximately 5V). Measure signal wire continuity from sensor connector to ECM pin using wiring diagrams.

Step 3: Hydraulic System Check Verify hydraulic oil level and condition—contaminated oil can damage sensors. Install a calibrated pressure gauge at the test port to confirm actual system pressure (normal operating range: 320-350 bar). If pressure readings are normal but the code persists, replace the pressure sensor.

Step 4: Sensor Replacement and Verification Install a genuine Komatsu replacement sensor (aftermarket sensors often cause recurring codes). Clear fault codes using Komatsu diagnostic software (KOMTRAX) or compatible scanner. Operate the machine through full hydraulic cycles and monitor for code recurrence.

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Disclaimer: This guide provides general troubleshooting information. Hydraulic systems operate under extreme pressure and require specialized knowledge. Always consult a qualified diesel mechanic or Komatsu-certified technician for complex diagnostics and repairs, especially on used equipment with unknown service history.