Komatsu PC210LC-7 Fault Code S-5: Complete Diagnostic Guide

What is Komatsu PC210LC-7 Fault Code S-5?

Fault Code S-5 on the Komatsu PC210LC-7 indicates a malfunction in the hydraulic pump flow control system, specifically related to the pump discharge pressure sensor circuit or the main relief valve control. This code is triggered when the Electronic Control Module (ECM) detects abnormal voltage signals or pressure readings from the hydraulic system monitoring components.

The PC210LC-7 utilizes a sophisticated closed-center hydraulic system with electronic flow control. This fault directly impacts the excavator's ability to regulate hydraulic pressure and flow efficiently, which is critical for precise operation and fuel economy. When S-5 activates, the machine typically enters a derate mode to prevent catastrophic damage to the hydraulic pump or main control valve.

Common Symptoms

When fault code S-5 is active, operators typically experience:

• Amber or red hydraulic warning light illuminated on the monitor panel
• Reduced hydraulic power across all functions (boom, arm, bucket, and swing)
• Sluggish or delayed response when operating multiple functions simultaneously
• Intermittent loss of hydraulic pressure during heavy lifting or digging operations
• Error message displayed on the multi-function monitor indicating hydraulic system fault

Potential Causes

The most common technical causes for S-5 on used PC210LC-7 excavators include:

• Pump discharge pressure sensor failure due to internal diaphragm rupture or contaminated hydraulic oil
• Corroded or loose wiring connections at the pressure sensor harness (known wear point near the main pump)
• Main relief valve sticking caused by contamination, worn spools, or pilot pressure issues
• ECM voltage supply problems affecting sensor reference voltage (typically 5V DC)
• Damaged wiring harness from rubbing against the pump mounting bracket (common on machines with 5,000+ hours)
• Contaminated hydraulic oil causing erratic pressure readings and sensor fouling

How to Troubleshoot and Fix Code S-5

Step 1: Connect Diagnostic Software Use Komatsu KOMTRAX or compatible diagnostic laptop with proper interface cables. Read active and stored codes, then monitor live data for pump discharge pressure readings. Normal operating pressure should be 320-350 bar (4,640-5,075 PSI).

Step 2: Inspect Pressure Sensor and Wiring Locate the pump discharge pressure sensor mounted on the main hydraulic pump. Check for:

• Physical damage, oil leaks, or corrosion on the sensor body
• Connector pins for bent terminals, moisture, or corrosion (use electrical contact cleaner)
• Harness routing for abrasion points where wires contact the pump housing or frame

Step 3: Perform Electrical Testing With ignition on, engine off, use a digital multimeter to verify:

• 5V reference voltage at sensor connector (ECM pin signal)
• Signal wire continuity from sensor to ECM (should read less than 2 ohms resistance)
• Ground circuit integrity with less than 0.5 ohms to chassis ground

Step 4: Test Hydraulic Components Install a calibrated pressure gauge at the test port. Start the engine and compare actual pressure against sensor readings in diagnostic software. A variance greater than 10 bar indicates sensor replacement is needed. If pressure fluctuates wildly, inspect the main relief valve for contamination or wear.

Step 5: Clear Codes and Test After repairs, clear fault codes and operate the machine under load for 20-30 minutes. Monitor for code recurrence and verify all hydraulic functions operate normally.

For used excavators specifically: Always inspect connector seals and apply dielectric grease to prevent moisture intrusion. Check hydraulic oil condition—contaminated oil is a leading cause of sensor and valve failures in older machines.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. If unfamiliar with hydraulic or electrical systems, contact a certified Komatsu technician to prevent injury or further equipment damage.