Komatsu PC100-6 Fault Code E308: Complete Diagnostic Guide

What is Komatsu PC100-6 Fault Code E308?

Fault Code E308 on the Komatsu PC100-6 indicates a malfunction in the travel motor system circuit, specifically an abnormal signal or electrical issue with the travel motor control solenoid valve. This code is triggered when the Electronic Control Module (ECM) detects incorrect voltage or current flow in the travel motor pilot solenoid circuit, preventing proper communication between the controller and the hydraulic travel system.

This fault is critical because the PC100-6's travel motors rely on precise solenoid valve operation to regulate hydraulic flow for forward/reverse movement and speed control. When E308 activates, the machine's mobility becomes compromised, directly impacting jobsite productivity and operator safety.

Common Symptoms

• Erratic or jerky travel movement in one or both tracks, particularly during forward or reverse operation
• Complete loss of travel function while swing and boom operations remain normal
• Intermittent warning light on the monitor panel, often appearing during cold starts or after extended operation
• Travel motor operates at reduced speed or fails to respond to pedal input
• Code reappears after clearing, especially on used machines with higher operating hours

Potential Causes

The most frequent causes of E308 on used PC100-6 excavators include:

• Damaged wiring harness along the undercarriage frame where cables experience constant flexing and exposure to debris
• Corroded connector pins at the travel motor solenoid valve, common in machines operated in wet or marine environments
• Failed travel motor solenoid valve due to internal coil breakdown (typical after 6,000-8,000 operating hours)
• ECM internal fault or voltage supply issues from the main power harness
• Contaminated hydraulic pilot pressure sensor causing incorrect signal feedback
• Worn connector seals allowing moisture intrusion at junction points near the final drive

How to Troubleshoot and Fix Code E308

Step 1: Visual Inspection
Examine the travel motor solenoid valve connector for corrosion, bent pins, or oil contamination. On used excavators, check the wiring harness routing from the ECM to the travel motors for abrasion points, particularly where cables contact the track frame or swing bearing area.

Step 2: Electrical Testing
Using a digital multimeter, measure resistance across the solenoid valve coil terminals (connector disconnected). Specification is typically 10-15 ohms at 20°C. Check for voltage supply at the connector with ignition on: should read 12-24V DC depending on circuit design. Inspect ground continuity to chassis.

Step 3: Signal Verification
With Komatsu diagnostic software (KOMTRAX or PC-based diagnostic tool), monitor real-time solenoid command signals while operating travel pedals. Compare left and right travel motor signals for discrepancies. Check pilot pressure sensor readings for abnormal values.

Step 4: Component Replacement
If testing confirms solenoid failure, replace the travel motor control valve assembly. For used machines, simultaneously replace the connector pigtail (Komatsu part 20Y-60-32120 or equivalent) to prevent recurring corrosion issues. Clear codes and perform operational test under load.

Critical for Used Equipment: Before parts replacement, apply dielectric grease to all cleaned connectors and secure harnesses with new protective loom where wear is evident. Many E308 codes on older PC100-6 machines resolve through connector service alone.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC100-6 service manual and consider professional technician assessment for complex electrical faults or safety-critical repairs.