What is Komatsu PC210-8 Fault Code DW91KA?

Fault code DW91KA on a Komatsu PC210-8 excavator indicates a communication error between the Engine Controller (ECM) and the Hydraulic Pump Controller (PPC). This diagnostic trouble code (DTC) specifically signals that the CAN (Controller Area Network) bus communication link has been interrupted or degraded between these two critical control modules.

The ECM and PPC must constantly exchange data to optimize engine performance and hydraulic system efficiency on the PC210-8. When communication fails, the machine cannot properly coordinate power delivery with hydraulic demand, which is essential for fuel economy and responsive operation. This code is particularly critical because the PC210-8 uses an integrated control system where engine output is dynamically matched to hydraulic load requirements through continuous controller communication.

Common Symptoms

When fault code DW91KA is active, operators typically experience:

• Warning lamp illumination on the monitor panel, often with a simultaneous error message displayed
• Reduced machine performance or derate mode, where engine power is automatically limited to protect components
• Sluggish hydraulic response during combined operations (swing and boom movements simultaneously)
• Intermittent loss of fine control over hydraulic functions, especially under heavy loads
• Engine may default to fixed RPM settings rather than auto-adjusting to hydraulic demand

Potential Causes

The most common technical causes for DW91KA on used PC210-8 excavators include:

• CAN bus wiring harness damage at known rub points near the engine firewall or along the right-side frame rail where harnesses pass through metal grommets
• Corroded or loose connector pins at the ECM (located under the operator cab) or PPC module (mounted near hydraulic pumps)
• Water intrusion into controller connectors due to deteriorated seals—common on machines with 5,000+ operating hours
• Failed termination resistors on the CAN bus network causing signal reflection
• ECM or PPC module internal failure, though less common than wiring/connector issues
• Low battery voltage or poor grounding connections affecting CAN bus signal integrity

How to Troubleshoot and Fix Code DW91KA

Step 1: Visual Inspection of Harnesses and Connectors Begin by inspecting the CAN bus wiring harness running between the ECM and PPC. On used excavators, check for wear points where the harness contacts the frame, especially near pivot points. Disconnect both ECM and PPC connectors and inspect pins for corrosion, bent contacts, or moisture. Clean connectors with electrical contact cleaner and apply dielectric grease before reconnecting.

Step 2: Test CAN Bus Signal Integrity Using a digital multimeter, measure the resistance between the CAN-High and CAN-Low wires at the ECM connector (typically pins should show 60 ohms with both controllers connected, indicating proper termination). Check for voltage fluctuations on the CAN lines with ignition on—should read approximately 2.5V at rest. Komatsu's KOMTRAX diagnostic software or a compatible J1939 CAN scanner can monitor real-time communication packets to identify dropout patterns.

Step 3: Check Power Supply and Grounding Verify that both the ECM and PPC are receiving clean 24V power supply. Test ground continuity from each controller case to battery negative—resistance should be below 0.5 ohms. On older machines, corrosion at ground points is a frequent cause of communication failures.

Step 4: Controller Replacement (If Necessary) If wiring and connections test good, the issue likely resides in one of the controllers. Swap testing with known-good units can isolate the failed component. For used excavators, always check service history—previous electrical repairs may have introduced poor crimps or aftermarket connectors that fail prematurely.

Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu PC210-8 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs can cause additional damage to expensive electronic modules.