Komatsu PC210LC-8 Fault Code S-6: Complete Diagnostic Guide

What is Komatsu PC210LC-8 Fault Code S-6?

Fault Code S-6 on the Komatsu PC210LC-8 indicates a malfunction in the engine controller (ECM) power supply circuit, specifically a voltage abnormality or interruption in the main relay system. This code triggers when the Electronic Control Module (ECM) detects irregular voltage input that falls outside the manufacturer's specified range of 20-32 volts during normal operation.

This fault is critical for the PC210LC-8 because the ECM relies on stable power to manage fuel injection timing, turbocharger boost control, and emissions systems on the SAA6D107E-1 engine. Any voltage irregularity can cause erratic engine performance, loss of power, or complete shutdown to protect engine components from damage.

Common Symptoms

When Code S-6 is active, operators typically experience:

• Engine fails to start or immediately shuts down after ignition
• Intermittent power loss during operation, especially under heavy loads
• Monitor display flickering or complete electrical system reset
• Warning lamp illumination on the instrument cluster with reduced engine output
• Hard starting conditions requiring multiple cranking attempts

Potential Causes

The most common technical failures triggering S-6 on used PC210LC-8 excavators include:

• Main relay failure due to contact wear or internal coil deterioration (common after 8,000+ operating hours)
• Corroded or loose battery terminals causing voltage drops during high-amperage draw
• Damaged wiring harness between the battery and ECM, particularly at the firewall pass-through where vibration causes insulation breakdown
• Failing alternator unable to maintain proper charging voltage (belt-driven models show wear on pulley bearings)
• ECM ground circuit degradation from corrosion at chassis ground points
• Faulty ignition switch contacts preventing consistent power delivery to the relay circuit

How to Troubleshoot and Fix Code S-6

Step 1: Verify Battery and Charging System Using a digital multimeter, check battery voltage with the engine off (should read 12.5-13V) and running (should read 13.8-14.4V). Inspect all battery cable connections for corrosion, particularly the negative ground to frame. On used machines, clean terminals with a wire brush and apply dielectric grease.

Step 2: Test Main Relay Operation Locate the main relay in the electrical panel beneath the operator cab. With ignition on, listen for an audible click. Measure voltage at relay terminals: Pin 30 should show battery voltage, Pin 87 should show voltage when energized. Replace relay if coil resistance measures outside 70-90 ohms.

Step 3: Inspect ECM Power Supply Harness Trace the power harness from the relay to the ECM connector (typically a 38-pin connector). Check for chafing damage where the harness contacts the chassis rail—a known wear point on PC210LC-8 models. Measure voltage at ECM pin 1 with ignition on; should read 24V ±2V. For used excavators, inspect connector pins for heat discoloration indicating intermittent connection.

Step 4: Ground Circuit Verification Check all ECM ground points at the engine block and frame. Remove, clean with sandpaper, and retorque to 15-20 ft-lbs. Perform a voltage drop test: should not exceed 0.2V between battery negative and ECM ground during cranking.

Professional Disclaimer: This guide provides general troubleshooting steps for Code S-6. Always consult the official Komatsu service manual for your specific serial number range and consider professional diagnostic software (Komatsu KOMTRAX or diagnostic tool) for complete system analysis before replacing expensive components.