What is Hitachi EX200-3 Fault Code 108-3?

Hitachi EX200-3 Fault Code 108-3 indicates a hydraulic pump control solenoid circuit malfunction, specifically detecting an abnormal voltage or open circuit in the main pump flow control system. This code is generated when the machine's Electronic Control Module (ECM) detects that the electrical signal to the hydraulic pump solenoid valve is outside the manufacturer's specified parameters (typically 0.5-4.5 volts).

This fault is critical for the EX200-3 because the hydraulic pump control directly regulates engine load matching and flow distribution to all hydraulic functions. When this circuit malfunctions, the excavator cannot properly adjust pump displacement based on operational demand, leading to poor fuel efficiency, overheating, and reduced machine productivity. On used excavators, this code frequently appears due to wire harness deterioration from years of vibration and exposure to hydraulic oil mist in the engine compartment.

Common Symptoms

• Sluggish hydraulic response across all functions (boom, arm, bucket, swing) with noticeably reduced cycle times
• Engine over-revving under light loads due to improper pump load sensing feedback
• Intermittent loss of hydraulic power followed by sudden recovery, especially when operating on uneven terrain
• Diagnostic warning lamp illuminated on the instrument panel (typically amber/yellow)
• Excessive fuel consumption as the engine cannot efficiently match pump output to load requirements

Potential Causes

The most common causes for Code 108-3 on used EX200-3 excavators include:

• Damaged wiring harness at the known rub point where the pump control cable passes near the engine mounting bracket (common failure area on high-hour machines)
• Failed hydraulic pump solenoid valve due to internal coil breakdown or contamination from degraded hydraulic fluid
• Corroded or loose connector pins at the ECM-to-solenoid harness junction (typically a 3-pin Deutsch connector)
• Faulty ECM output driver circuit (less common, but possible on machines with 8,000+ operating hours)
• Voltage supply issues from deteriorated ground connections on the main pump housing

How to Troubleshoot and Fix Code 108-3

Step 1: Visual Inspection and Connector Check Begin by inspecting the pump control solenoid connector located on the main hydraulic pump assembly. Disconnect the 3-pin connector and examine for corrosion, bent pins, or hydraulic oil contamination. On used excavators, this connector frequently shows green corrosion due to moisture intrusion. Clean contacts with electrical contact cleaner and apply dielectric grease.

Step 2: Electrical Testing with Multimeter Using a digital multimeter, check solenoid coil resistance. Disconnect the solenoid and measure across the coil terminals—resistance should read between 18-22 ohms at room temperature. Next, with the ignition on (engine off), backprobe the harness connector and verify the ECM is supplying approximately 12 volts to the solenoid power wire (typically the red wire). Check ground continuity to ensure less than 0.5 ohms resistance to chassis ground.

Step 3: Harness Inspection and Repair Trace the wiring harness from the ECM (located under the operator's cab) to the hydraulic pump. Pay special attention to the section passing along the engine block where heat and vibration cause insulation breakdown. On used EX200-3 machines, the harness often rubs against the engine mount bracket. Look for exposed copper wire or melted insulation. Repair damaged sections with heat-shrink tubing and reroute away from contact points using proper cable ties.

Step 4: Solenoid Replacement and Calibration If electrical tests confirm solenoid failure, replace with a genuine Hitachi pump control solenoid (Part# 4448336 or equivalent). After installation, clear fault codes using Hitachi Dr.EX diagnostic software or a compatible scanner. Perform a pump calibration procedure per the service manual to ensure proper ECM communication.

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Hitachi EX200-3 service manual for complete specifications and safety procedures. If you're unfamiliar with hydraulic systems or electrical diagnostics, consult a certified Hitachi technician to prevent equipment damage or personal injury.