Komatsu PC210-8M0 Fault Code DW91KB: Meaning and Fix

What is Komatsu PC210-8M0 Fault Code DW91KB?

Fault code DW91KB indicates a communication error between the engine ECM (Engine Control Module) and the hydraulic system's pump controller, specifically related to pump flow control signal abnormality.

This diagnostic trouble code (DTC) signals that the engine control unit is not receiving proper feedback from the pump flow control solenoid or its associated circuitry. The Komatsu PC210-8M0 relies on precise communication between the engine management system and hydraulic pump controller to optimize fuel efficiency and hydraulic performance. When this communication fails, the machine cannot properly match engine power to hydraulic demand, resulting in reduced operational efficiency and potential component damage if left unaddressed.

Common Symptoms

• Yellow warning light illuminated on the instrument panel with reduced hydraulic response
• Sluggish hydraulic performance across all circuits, particularly noticeable during combined operations
• Engine derate mode activated, limiting maximum RPM to approximately 1,800-2,000 RPM
• Erratic pump displacement causing inconsistent swing speed or boom/arm movements
• Intermittent loss of power during high-demand operations like digging or lifting

Potential Causes

Electrical connector corrosion at the pump flow control solenoid is the most common culprit in used machines, particularly those operated in wet or coastal environments. The connector pin terminals deteriorate over time, creating intermittent signal interruption.

Wiring harness damage between the ECM and pump controller often occurs at known rub points near the engine mount area and along the left-hand chassis frame rail where vibration causes insulation wear.

Pump flow control solenoid failure due to internal coil breakdown or valve contamination from degraded hydraulic fluid in machines with 5,000+ operating hours.

ECM internal fault (less common) where the controller's output driver circuit has failed, preventing proper voltage supply to the solenoid.

Hydraulic fluid contamination causing the proportional valve within the pump control system to stick or respond erratically.

How to Troubleshoot and Fix Code DW91KB

Step 1: Visual Inspection Begin by inspecting the pump flow control solenoid connector located on the main hydraulic pump assembly. Remove the connector and examine both male and female terminals for green corrosion, bent pins, or moisture intrusion. Clean terminals with electrical contact cleaner and dielectric grease before reconnection.

Step 2: Electrical Testing Using a multimeter, check for proper voltage supply at the solenoid connector with the key in the ON position. You should measure approximately 12-14V DC. Next, measure solenoid resistance, which should read between 10-15 ohms. Values outside this range indicate solenoid replacement is necessary.

Step 3: Harness Continuity Check Trace the wiring harness from the ECM (located behind the cab, right side) to the pump controller. Pay special attention to the harness routing near the engine mounting brackets where abrasion commonly occurs in used excavators. Check for continuity and resistance on all signal wires; readings should be less than 5 ohms with no shorts to ground.

Step 4: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or an equivalent scan tool to monitor live pump control signal data. Compare actual versus commanded pump displacement percentages during operation. Discrepancies greater than 10% indicate controller or mechanical pump issues.

Step 5: Used Equipment Considerations For machines with high hours, remove and inspect the pump flow control valve assembly for varnish buildup or mechanical wear. Disassemble, clean with hydraulic system cleaner, and verify free movement before reinstalling.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic services for complex electrical or hydraulic system repairs.