What is Komatsu PC220-8 Fault Code DW91KA?

Fault Code DW91KA on the Komatsu PC220-8 excavator indicates a malfunction in the hydraulic pump control system, specifically related to the pump flow control solenoid valve circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal electrical signal or resistance value outside manufacturer specifications in the pump proportional solenoid circuit.

The Komatsu PC220-8 uses a sophisticated closed-center hydraulic system with electronic control over pump displacement. The pump flow control solenoid regulates hydraulic oil flow based on operator demand and load sensing. When DW91KA appears, the machine's ability to efficiently match hydraulic power to work requirements is compromised, directly impacting fuel efficiency and operational performance. This code is particularly critical because it can force the excavator into a derated mode, limiting productivity on job sites.

Common Symptoms

When DW91KA is active on your PC220-8, operators typically experience:

• Illuminated warning lamp on the monitor panel with fault code display
• Sluggish hydraulic response across all functions (boom, arm, bucket, swing)
• Reduced digging force and slower cycle times, especially under heavy loads
• Inconsistent engine RPM fluctuations during combined hydraulic operations
• Increased fuel consumption due to inefficient pump control and constant high-flow operation

Potential Causes

The most common technical reasons for DW91KA on used PC220-8 excavators include:

• Solenoid valve coil failure due to internal short circuit or open winding (resistance outside 8-12 ohm specification)
• Wiring harness damage at known rub points near the main pump mounting area or along the right-hand chassis rail
• Corroded or loose connectors on the solenoid harness, particularly the 3-pin Deutsch connector near the pump assembly
• ECM internal fault affecting the solenoid driver circuit (less common but occurs in high-hour machines)
• Voltage supply issues from the main power harness, including damaged fuses or relay contacts
• Contaminated hydraulic oil causing mechanical sticking of the solenoid spool valve

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection and Connector Check Begin by accessing the main hydraulic pump located on the left side of the engine. Inspect the pump flow control solenoid and its wiring harness for obvious damage, oil contamination, or connector corrosion. On used excavators, pay special attention to harness routing where it passes over the pump—this is a known wear point on PC220-8 models. Clean all connectors with electrical contact cleaner and check for pushed-back pins.

Step 2: Electrical Testing Using a digital multimeter, disconnect the solenoid connector and measure coil resistance across the solenoid terminals. Specification should be 8-12 ohms at 20°C. Next, check for supply voltage at the harness connector with the ignition on—you should see battery voltage (24V nominal). Check for continuity between the solenoid ground terminal and machine chassis ground (should be less than 1 ohm).

Step 3: Solenoid Function Test If resistance is within specification, perform a functional test using Komatsu KOMTRAX diagnostic software or a compatible diagnostic laptop interface. Command the solenoid to actuate while monitoring current draw—it should be 1.8-2.2 amps. Listen and feel for solenoid clicking, indicating mechanical movement. If electrical values are correct but no mechanical action occurs, the solenoid valve is likely mechanically stuck or internally damaged.

Step 4: Harness and ECM Verification If the solenoid tests good, trace the harness back to the ECM (located under the operator cab floor). Check for voltage drops along the harness using voltage drop testing while the circuit is energized—drops exceeding 0.5V indicate resistance from corrosion or damaged wiring. Inspect the ECM connector pins for corrosion, especially on used machines with 5,000+ hours.

Step 5: Component Replacement and Verification Replace failed components—the pump flow control solenoid (part number 702-21-57400) is the most common fix for DW91KA. After replacement, clear the fault code using diagnostic software, cycle the ignition, and operate all hydraulic functions under load. Monitor for code reoccurrence. On used excavators, always replace the solenoid connector pigtail if any corrosion or heat damage was present.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC220-8 DW91KA fault code. Always consult the official Komatsu service manual for your specific machine serial number and software version. If you're unfamiliar with electrical diagnostics or hydraulic systems, seek assistance from a certified Komatsu technician to prevent equipment damage or safety hazards.