Komatsu HB215LC-1 Fault Code E-35: Meaning and Fix

What is Komatsu HB215LC-1 Fault Code E-35?

Fault Code E-35 on the Komatsu HB215LC-1 hybrid excavator indicates a malfunction in the swing motor resolver system or swing motor control circuit. This code specifically points to communication errors or signal abnormalities between the swing motor resolver (position sensor) and the inverter control unit.

The HB215LC-1 uses an advanced hybrid system where the swing motor operates as both a motor and generator. The resolver provides precise positional feedback to the inverter, which is essential for regenerative braking and smooth swing operation. When this feedback signal fails or becomes erratic, the ECM (Engine Control Module) logs E-35 to prevent damage to expensive hybrid components and ensure operator safety.

This fault is particularly critical because it directly affects the machine's ability to capture and store energy during swing deceleration—one of the primary fuel-saving features of this hybrid model.

Common Symptoms

• Swing function completely disabled or operates only in limited capacity without regeneration
• Hybrid system warning lamp illuminated on the monitor panel (often amber or red)
• Reduced swing speed or jerky, inconsistent swing motion during operation
• Error message displayed on the multi-information display indicating swing system fault
• Loss of fuel economy as the regenerative swing system fails to capture braking energy

Potential Causes

On used Komatsu HB215LC-1 machines, E-35 typically stems from:

• Resolver connector corrosion or moisture intrusion at the swing motor housing connection—common on machines with 5,000+ hours
• Damaged resolver wiring harness due to rubbing against the swing bearing race or center joint area
• Failed swing motor resolver itself (rare but possible after extreme vibration or impact)
• Inverter control unit communication failure caused by voltage irregularities or internal board degradation
• Loose or corroded grounding points on the uppercarriage frame affecting signal integrity
• Damaged swing motor assembly allowing resolver misalignment or physical damage

How to Troubleshoot and Fix Code E-35

Step 1: Visual Inspection of Resolver and Wiring Access the swing motor resolver connector located on the swing motor assembly beneath the cab platform. Inspect for visible corrosion, bent pins, or water contamination. Check the entire harness routing from the swing motor to the inverter unit (typically mounted behind the cab) for chafing, cuts, or damage from the rotating uppercarriage.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, check resolver winding resistance. The typical specification calls for approximately 50-150 ohms between resolver coil terminals (consult the specific service manual for exact values). Also verify reference voltage from the inverter to the resolver—should read approximately 5-8 volts DC. Any significant deviation indicates a faulty resolver or inverter issue.

Step 3: Connector Cleaning and Secure Connections For used excavators, connector corrosion is the most common culprit. Disconnect the resolver connector, clean with electrical contact cleaner, and apply dielectric grease before reconnection. Ensure all locking tabs engage fully and check that the ground wire connection at the swing motor case is tight and corrosion-free.

Step 4: Diagnostic Software Verification Connect Komatsu KOMTRAX diagnostic software or compatible scan tool to read real-time resolver signal data. Monitor the sine/cosine wave outputs while manually rotating the swing motor (engine off). Irregular waveforms confirm resolver failure; no signal suggests wiring or inverter problems.

Step 5: Component Replacement Priority If basic cleaning and connection repairs don't resolve E-35, replace components in this order: (1) Resolver wiring harness (especially if visible wear exists), (2) Swing motor resolver sensor, (3) Inverter control unit (requires dealer programming in most cases).

For used machinery, always inspect for previous repair attempts or modifications to the hybrid system that may have introduced wiring errors or incompatible components.

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Disclaimer: This guide provides general troubleshooting information for Komatsu HB215LC-1 fault code E-35. Hybrid excavator systems involve high-voltage components that require specialized training. Always consult the official Komatsu service manual and consider professional assistance from certified Komatsu technicians, especially when working with inverter and high-voltage electrical systems.