Komatsu PC800SE-8R Fault Code E-33: Complete Diagnostic Guide

What is Komatsu PC800SE-8R Fault Code E-33?

Fault Code E-33 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the engine control module (ECM). This code specifically relates to the coolant temperature monitoring system, which is critical for preventing engine overheating and maintaining optimal operating temperatures in the SAA6D170E-5 engine.

The ECM continuously monitors coolant temperature through a thermistor-type sensor that changes resistance based on temperature. When the sensor signal falls outside predetermined parameters—either showing implausibly high/low readings or circuit irregularities—the system triggers E-33. For the PC800SE-8R, this is particularly critical because improper temperature management can lead to reduced hydraulic efficiency, engine derate, and potential catastrophic engine damage in high-demand excavation operations.

Common Symptoms

When Code E-33 is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by an audible alarm
• Engine derate mode where maximum RPM is limited to protect the engine from potential overheating
• Inaccurate temperature gauge readings showing extreme high or low temperatures that don't match actual engine conditions
• Difficulty starting in cold conditions if the ECM receives false cold-temperature signals
• Intermittent code activation that may clear and return, especially during machine warm-up cycles

Potential Causes

The most common technical causes for E-33 in used PC800SE-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or internal element breakdown
• Wiring harness damage at known rub points near the engine block where vibration causes insulation wear
• Corroded or loose connector pins at the sensor plug, particularly common in machines operating in wet or corrosive environments
• ECM internal circuit issues affecting the temperature monitoring input channel
• Coolant contamination causing sensor element coating and inaccurate readings
• Ground circuit problems creating voltage reference issues in the sensor circuit

How to Troubleshoot and Fix Code E-33

Step 1: Visual Inspection Begin by locating the coolant temperature sensor on the engine block (typically near the thermostat housing). Inspect the wiring harness for obvious damage, chafing, or exposure at mounting brackets and routing points. Check the connector for corrosion, bent pins, or moisture intrusion—common issues in used excavators with 5,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult Komatsu specifications). Test circuit continuity from the sensor connector back to the ECM. Check for short circuits to ground by measuring resistance between signal wire and chassis ground (should read infinite resistance).

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to monitor real-time temperature readings. Compare sensor output against actual coolant temperature using an infrared thermometer. A variance exceeding 15°F indicates sensor replacement is necessary.

Step 4: Component Replacement If testing confirms sensor failure, replace with a genuine Komatsu sensor (part number specific to SAA6D170E-5 engine). For used machines, always apply dielectric grease to connector pins and secure harness routing to prevent future chafing. Clear codes and perform a heat cycle test to verify repair.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional technician assistance for complex electrical diagnostics or ECM-related issues.