Komatsu PC110-8M0 Fault Code S-13: Complete Diagnostic Guide

What is Komatsu PC110-8M0 Fault Code S-13?

Fault Code S-13 on the Komatsu PC110-8M0 excavator indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the engine control module (ECM).

This diagnostic trouble code specifically monitors the engine coolant temperature sensor (also called the water temperature sensor) and its associated wiring harness. The ECM continuously reads voltage signals from this sensor to regulate fuel injection timing, idle speed, and prevent engine overheating. On the PC110-8M0's SAA4D95LE-5 engine, this sensor is critical because improper temperature readings can cause poor combustion efficiency, increased emissions, and potential engine damage. When the ECM detects voltage readings outside the normal range (typically 0.5-4.5 volts), it triggers S-13 and may activate protective engine derating.

Common Symptoms

When fault code S-13 is active on your Komatsu PC110-8M0, operators typically experience:

• Engine warning light illuminated on the instrument panel (often amber or red)
• Erratic temperature gauge readings that fluctuate abnormally or read maximum temperature immediately after cold start
• Difficult cold starting or extended cranking time, especially in cooler weather
• Rough idle or inconsistent engine RPM during warm-up phase
• Automatic engine derate (reduced power output) as a protective measure if the ECM assumes overheating conditions

Potential Causes

The most common technical causes for S-13 on used PC110-8M0 excavators include:

• Failed coolant temperature sensor due to internal element degradation (common after 5,000+ operating hours)
• Damaged or corroded wiring harness connections at the sensor plug, particularly where the harness routes near the engine block and experiences heat cycling
• Chafed sensor wiring caused by contact with engine components or mounting brackets—a known wear point on PC110 series machines
• Corroded or loose ground connections in the engine harness, especially on machines operated in wet or marine environments
• ECM internal fault (rare, but possible on high-hour machines with previous electrical issues)
• Coolant contamination causing sensor tip fouling or deposits affecting readings

How to Troubleshoot and Fix Code S-13

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the connector pins. On used excavators, carefully examine the entire wiring harness from the sensor to the ECM for chafing, especially where it passes near moving components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 68°F (20°C), resistance should be approximately 2,000-3,000 ohms (consult your service manual for exact specifications). Test the harness continuity by checking resistance from the ECM connector to the sensor connector—it should read less than 1 ohm. Also verify the 5-volt reference signal from the ECM with the ignition on.

Step 3: Sensor Replacement and System Reset If testing confirms sensor failure, replace it with a genuine Komatsu part (part number 6732-81-3160 or equivalent). Apply anti-seize compound to threads and torque to specification (typically 15-20 ft-lbs). On used machines, always replace the connector pigtail if corrosion is present—this prevents repeat failures. Clear the fault code using Komatsu diagnostic software (KOMTRAX Plus) or a compatible scan tool, then run the engine through a complete heat cycle to verify the repair.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number. If you're unfamiliar with electrical diagnostics or lack proper tools, consult a certified Komatsu technician to prevent misdiagnosis or additional damage.