What is Komatsu PC210-10 Fault Code L01DW91KB?

Fault Code L01DW91KB on the Komatsu PC210-10 excavator indicates a communication error or malfunction within the machine's control network, specifically related to the CAN (Controller Area Network) bus system connecting the engine ECM (Engine Control Module) and the machine controller. This diagnostic trouble code signals that data transmission between critical control units has been interrupted or compromised, preventing proper coordination between the engine management system and hydraulic/operational controls.

This code is particularly critical for the PC210-10 because this model relies heavily on integrated electronic control systems to optimize fuel efficiency, hydraulic response, and emission compliance. When communication between controllers fails, the machine may enter a derate mode or experience reduced performance to protect components from potential damage due to uncoordinated system operation.

Common Symptoms

When fault code L01DW91KB is active, operators typically experience:

• Illuminated warning lights on the monitor panel, often accompanied by error messages indicating communication failure
• Reduced engine power or hydraulic response, as the system enters protective derate mode
• Intermittent or complete loss of monitor display functions, including fuel gauge, hour meter, or system status indicators
• Erratic operation of implements or travel functions due to inconsistent signal transmission
• Engine starting issues or unexpected shutdowns when communication cannot be established between control modules

Potential Causes

The most common technical reasons for L01DW91KB appearing on used PC210-10 excavators include:

• Damaged or corroded CAN bus wiring harness, particularly at known rub points near the engine firewall, swing bearing, or along the boom base where cable movement causes friction
• Faulty ECM or machine controller connectors with pushed-back pins, moisture intrusion, or oxidation buildup
• Defective terminating resistors on the CAN network (typically 120-ohm resistors at network endpoints)
• ECM or machine controller internal failure, though less common than wiring issues in used machines
• Voltage supply problems to control modules due to corroded battery connections, failing alternator, or poor ground connections
• Software version mismatch between controllers after component replacement or incomplete updates

How to Troubleshoot and Fix Code L01DW91KB

Step 1: Visual Inspection of CAN Bus Harness Begin by thoroughly inspecting the CAN bus communication cables (typically twisted-pair orange/green wires on Komatsu machines) from the ECM to the machine controller. Check for obvious damage, especially at known wear points: where harnesses pass through the revolving frame, near hydraulic lines, and at connector entry points. Look for chafing, cuts, or burn marks that could cause intermittent shorts.

Step 2: Connector and Pin Integrity Check Disconnect the main harness connectors at both the engine ECM (located near the engine right side) and the machine controller (typically under the operator cab floor). Inspect for:

• Corrosion or oxidation on pins (common in used excavators exposed to moisture)
• Bent or pushed-back pins that may not make proper contact
• Moisture or oil contamination inside connector housings Clean connectors with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 3: CAN Bus Voltage and Resistance Testing Using a digital multimeter, measure the resistance between CAN-High and CAN-Low terminals at the ECM connector with all modules disconnected. You should read approximately 60 ohms (two 120-ohm terminating resistors in parallel). Readings significantly higher suggest an open circuit in the network or missing terminating resistor. With the key on and harness reconnected, measure voltage between CAN-High and ground (should be approximately 2.5-3.5V) and CAN-Low and ground (approximately 1.5-2.5V).

Step 4: Test with Komatsu KOMTRAX or Diagnostic Software Connect Komatsu diagnostic software (KOMTRAX Plus or dealer-level diagnostics) to monitor real-time CAN bus communication status. This will help identify whether the failure is constant or intermittent, and which specific controller is dropping off the network. Check for additional fault codes that may indicate the root cause.

Step 5: Check Ground Connections and Power Supply Poor grounds are frequently overlooked causes in used excavators. Verify that all chassis ground points are clean, tight, and free of corrosion. Check battery voltage (should be 12.5-13V key off, 13.8-14.4V running) and verify proper voltage at both ECM and machine controller power supply pins.

Step 6: Component Replacement (If Necessary) If wiring and connections check out, the issue may be internal to a controller. Before replacing expensive control modules on a used machine, consider swapping with a known-good unit if available for testing. Always ensure software compatibility when replacing controllers, as version mismatches can cause communication errors.

Critical Note for Used Excavators: Due to years of vibration, temperature cycling, and moisture exposure, harness and connector issues are far more common than actual controller failures. Always thoroughly verify wiring integrity and connection quality before condemning electronic modules.

---

Disclaimer: This guide provides general troubleshooting information for diagnostic purposes. Always consult the official Komatsu PC210-10 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs to electronic control systems can cause further damage or create safety hazards.