Komatsu PC110-7 Fault Code E-23: Complete Diagnostic Guide

What is Komatsu PC110-7 Fault Code E-23?

Fault Code E-23 on the Komatsu PC110-7 indicates a malfunction in the engine coolant temperature sensor circuit or an out-of-range coolant temperature reading. This code is triggered when the ECM (Engine Control Module) detects abnormal voltage signals from the coolant temperature sensor, typically indicating a short circuit, open circuit, or implausible temperature reading.

The coolant temperature sensor is critical for the PC110-7's SAA4D95LE-3 engine management system. It directly affects fuel injection timing, engine warm-up cycles, and prevents overheating damage. When this sensor fails, the ECM cannot properly regulate engine temperature, potentially leading to reduced performance, increased emissions, or catastrophic engine damage if undetected.

Common Symptoms

When Code E-23 is active on your Komatsu PC110-7, operators typically experience:

• Engine warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Engine derate mode where maximum RPM is limited to protect the engine
• Difficult cold starts or extended cranking time before the engine fires
• Rough idle particularly when the engine is cold, smoothing out as it warms
• Erratic temperature gauge readings showing unusually high, low, or fluctuating temperatures

Potential Causes

The most common technical failures causing E-23 on used PC110-7 excavators include:

• Failed coolant temperature sensor due to age-related internal resistance drift (extremely common on machines with 5,000+ hours)
• Corroded or damaged wiring harness at the sensor connector, particularly where the harness passes near the hydraulic pump mounting bracket (known rub point)
• Shorted sensor wiring caused by chafing against the engine block or exhaust manifold heat shield
• Poor ground connection at the sensor or ECM grounding points due to corrosion buildup
• Contaminated coolant causing sensor element coating or failure
• ECM internal fault (rare, but possible on machines stored in high-humidity environments)

How to Troubleshoot and Fix Code E-23

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block near the thermostat housing. Check for coolant leaks, corrosion on the connector pins, or damaged wiring. On used excavators, carefully examine where the sensor harness routes alongside the hydraulic lines—friction wear is extremely common here.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms. At 176°F (80°C), it should drop to 200-400 ohms. Readings outside this range indicate sensor failure. Also check for 5-volt reference voltage at the harness connector with the sensor disconnected and ignition on.

Step 3: Wiring and Ground Verification Test the sensor harness for continuity from the sensor connector to the ECM. Check for shorts to ground or power. Clean and tighten all ground connections at the engine block and ECM mounting points, as corrosion buildup is prevalent on older machines.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu part (6732-81-3140) or verified OEM-equivalent. After installation, clear codes using Komatsu diagnostic software (KOMTRAX) or a compatible scanner, then perform a test run to verify repair.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu PC110-7 service manual and consider professional diagnostic assistance for complex electrical issues or if you're unfamiliar with excavator electrical systems.