What is Komatsu PC110-7 Fault Code E-29?

Fault Code E-29 on the Komatsu PC110-7 excavator indicates a malfunction in the hydraulic oil temperature sensor circuit or an abnormal hydraulic oil temperature reading. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects either an open circuit, short circuit, or implausible voltage signal from the hydraulic oil temperature sensor located in the hydraulic tank.

This code is critical for the PC110-7's performance because hydraulic oil temperature directly affects viscosity, system efficiency, and component longevity. When the ECM cannot accurately monitor hydraulic temperature, it may initiate protective measures that limit machine performance or prevent operation entirely to avoid catastrophic hydraulic system damage.

Common Symptoms

When Code E-29 is active on your Komatsu PC110-7, operators typically experience:

• Warning light illumination on the instrument panel, often accompanied by an audible alarm
• Reduced hydraulic performance or complete loss of hydraulic functions as the system enters a protective derate mode
• Erratic temperature gauge readings showing unusually high, low, or fluctuating hydraulic oil temperatures
• Intermittent code activation that comes and goes, especially during cold starts or after extended operation
• Machine shutdown in severe cases where the ECM interprets dangerously high temperature readings

Potential Causes

The most common technical causes for E-29 on used PC110-7 excavators include:

• Faulty hydraulic oil temperature sensor due to age-related failure or contamination from metallic debris in the hydraulic system
• Damaged or corroded wiring harness between the sensor and ECM, particularly at connector pins which are vulnerable to moisture intrusion
• Harness chafing at known wear points near the hydraulic tank mounting brackets or along the undercarriage routing path
• Poor electrical connections at the sensor connector or ECM terminals caused by corrosion, dirt, or loose pins
• ECM internal faults (less common) affecting the temperature sensor input circuit
• Actual hydraulic overheating due to clogged coolers, low oil levels, or excessive system loads triggering legitimate high-temperature warnings

How to Troubleshoot and Fix Code E-29

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor on the hydraulic tank (typically mounted on the side or bottom). Inspect the sensor body for physical damage, oil leaks, or contamination. Carefully examine the entire wiring harness from the sensor to the ECM, paying special attention to areas where the harness contacts metal edges, hydraulic lines, or frame members—common rub points on used excavators.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check sensor resistance. At room temperature (20°C/68°F), the sensor should typically read between 2,000-3,000 ohms (consult your service manual for exact specifications). Test harness continuity between the sensor connector and ECM pins—you should have less than 5 ohms resistance. Check for shorts to ground by measuring resistance between each wire and chassis ground (should read open circuit/infinite resistance).

Step 3: Voltage and Signal Testing With the ignition on but engine off, measure reference voltage at the sensor connector—typically 5 volts from the ECM. If voltage is absent or incorrect, the issue likely resides in the harness or ECM. For used machines, remove connectors and inspect for green corrosion, bent pins, or moisture—clean with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 4: Component Replacement and Verification If sensor resistance is out of specification or the harness shows damage, replace the faulty component with genuine Komatsu parts to ensure proper calibration. After repairs, clear the code using Komatsu diagnostic software (KOMTRAX) or a compatible scanner, then operate the machine through several temperature cycles to verify the fix. For persistent codes on used excavators, consider replacing both the sensor and harness simultaneously, as age-related degradation often affects multiple components.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific serial number and consider professional diagnostic services for complex electrical issues or if you're unfamiliar with high-voltage systems.