Komatsu PC35MR-2 Fault Code E-6: Complete Diagnostic Guide

What is Komatsu PC35MR-2 Fault Code E-6?

Fault Code E-6 on the Komatsu PC35MR-2 indicates an Engine Speed Sensor (RPM sensor) malfunction or signal error. This code triggers when the Engine Control Module (ECM) detects an abnormal or missing signal from the engine speed sensor, which monitors crankshaft rotation to calculate RPM and timing parameters.

The engine speed sensor is critical for proper fuel injection timing, governor control, and overall engine management on this compact excavator. Without accurate RPM data, the ECM cannot optimize performance, potentially causing erratic engine behavior or even preventing startup. On used Komatsu PC35MR-2 machines, this code frequently appears due to sensor degradation, wiring issues, or connector corrosion from years of exposure to dirt, moisture, and vibration.

Common Symptoms

When Code E-6 is active, operators typically experience:

• Engine cranks but fails to start, or starts and immediately stalls
• Erratic or unstable idle with noticeable RPM fluctuations
• Loss of engine power or failure to reach full throttle
• Warning light illuminated on the instrument panel (check engine light)
• Intermittent engine shutdown during operation, especially under load

Potential Causes

The most common technical reasons for E-6 fault codes on used PC35MR-2 excavators include:

• Failed engine speed sensor due to internal component wear or heat damage
• Damaged sensor wiring harness, particularly at flex points near the engine mount where vibration causes wire fatigue
• Corroded or loose sensor connector from moisture intrusion over years of service
• Broken or damaged reluctor ring (toothed wheel) on the crankshaft or flywheel
• ECM internal fault or poor ground connections affecting signal interpretation
• Debris accumulation between the sensor tip and reluctor ring affecting magnetic field detection

How to Troubleshoot and Fix Code E-6

Step 1: Visual Inspection Locate the engine speed sensor (typically mounted on the engine block near the flywheel housing). Inspect the sensor connector for corrosion, bent pins, or moisture. Check the wiring harness from sensor to ECM for rubbing, cuts, or signs of repair—common wear points include cable ties and engine mount areas.

Step 2: Sensor Resistance Test Disconnect the sensor connector and use a digital multimeter to measure resistance across the sensor terminals. Typical resistance should be 150-300 ohms (consult your service manual for exact specifications). Readings outside this range indicate sensor failure requiring replacement.

Step 3: Signal Voltage Check Reconnect the sensor and back-probe the connector wires while cranking the engine. You should see an AC voltage signal (typically 0.5-5V AC fluctuating). No signal indicates a dead sensor or air gap issue between sensor and reluctor ring.

Step 4: Air Gap and Reluctor Inspection Check the air gap between the sensor tip and reluctor ring (specification typically 0.5-1.5mm). On used excavators, inspect the reluctor ring for missing teeth, damage, or excessive buildup. Clean debris carefully with a non-metallic brush.

Step 5: Wiring Continuity and Ground Testing Test continuity from sensor connector to ECM pins using wiring diagrams. Check for shorts to ground or voltage. Verify ECM ground connections are clean and tight—corrosion here causes numerous sensor codes on older machines.

Step 6: Clear Code and Test After repairs, clear the fault code using Komatsu diagnostic software or by disconnecting the battery for 30 seconds. Run the machine through startup and load cycles to confirm proper operation.

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Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu PC35MR-2 service manual for exact specifications and safety procedures. For persistent issues or if you're uncomfortable with electrical diagnostics, consult a certified Komatsu technician or qualified heavy equipment mechanic.