Komatsu PC110-7 Fault Code E-33: Complete Diagnostic Guide

What is Komatsu PC110-7 Fault Code E-33?

Fault Code E-33 on the Komatsu PC110-7 excavator indicates a malfunction in the hydraulic oil temperature sensor circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the temperature sensor monitoring hydraulic fluid temperature in the main circuit.

The hydraulic oil temperature sensor plays a critical role in the PC110-7's performance management system. When hydraulic oil exceeds safe operating temperatures (typically above 90-95°C or 194-203°F), the ECM relies on this sensor to activate warning systems and implement protective measures. For used excavators, this sensor's accuracy is vital for preventing catastrophic hydraulic system damage, including seal degradation, oil breakdown, and reduced component lifespan.

Common Symptoms

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

• Warning light illumination on the instrument cluster (hydraulic oil temperature indicator flashing or solid)
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Machine derate or reduced hydraulic response as the ECM enters protective mode
• Intermittent alarms that may disappear when the machine cools down, indicating potential wiring issues
• No temperature reading displayed on the monitor, showing "---" or error symbols

Potential Causes

The most common technical causes for E-33 on used PC110-7 excavators include:

• Damaged or corroded sensor connector at the hydraulic tank (common on machines with 5,000+ hours due to exposure to moisture and vibration)
• Failed hydraulic oil temperature sensor with internal resistance drift or open circuit
• Wiring harness chafing where the sensor cable routes near the hydraulic tank or swing bearing—a known wear point on this model
• Poor ground connection at the sensor mounting point due to rust or paint buildup
• ECM internal fault (rare, but possible in high-hour machines with electrical system histories)
• Contaminated connectors from hydraulic oil mist accumulation in the engine compartment

How to Troubleshoot and Fix Code E-33

Step 1: Visual Inspection Begin with the sensor connector located on the hydraulic oil tank (typically left side of machine). Disconnect and inspect for corrosion, bent pins, or oil contamination. On used excavators, carefully check the entire wiring harness from sensor to ECM for abrasion points, especially where it passes through grommets or near moving components.

Step 2: Sensor Resistance Testing Using a digital multimeter, measure sensor resistance. Disconnect the sensor and check resistance across its terminals. At 20°C (68°F), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Compare readings at different temperatures. A reading of infinite resistance indicates an open circuit; near-zero indicates a short.

Step 3: Circuit Voltage Check With ignition on and sensor connected, back-probe the signal wire at the connector using a multimeter. You should see approximately 5V reference voltage from the ECM. If voltage is absent, trace the harness for breaks or check ECM connector terminals for corrosion.

Step 4: Ground Circuit Verification Verify continuity between the sensor ground terminal and chassis ground. Clean the sensor mounting boss with a wire brush to ensure proper grounding—critical on older machines where paint and oxidation accumulate.

Step 5: Replacement and Reset If diagnostics confirm sensor failure, replace with a genuine Komatsu sensor (part number specific to PC110-7). Aftermarket sensors may have incorrect resistance curves. After replacement, clear codes using Komatsu diagnostic software (KOMTRAX) or by disconnecting battery for 30+ minutes.

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Disclaimer: This guide provides general diagnostic information. Hydraulic and electrical systems contain hazardous components. Always consult the official Komatsu PC110-7 service manual and consider professional diagnostic assistance, especially for complex electrical issues or if you lack proper diagnostic equipment.