What is Komatsu PC110-8M0 Fault Code DWJ0KA?

Fault Code DWJ0KA on the Komatsu PC110-8M0 indicates a communication error between the machine's Engine Control Module (ECM) and the Hydraulic Control Unit (HCU). This diagnostic trouble code (DTC) is triggered when the CAN bus communication network experiences intermittent or complete signal loss between these critical control systems.

The PC110-8M0 relies on real-time data exchange between the ECM and HCU to optimize engine performance while coordinating hydraulic power distribution. When communication fails, the machine cannot properly regulate fuel delivery, engine speed, or hydraulic flow based on load demands. This fault is particularly critical because it directly impacts machine efficiency, can cause erratic hydraulic behavior, and may trigger automatic engine derate or shutdown modes to prevent equipment damage.

Common Symptoms

• Yellow or red warning lights illuminated on the instrument panel, often with reduced engine power
• Erratic hydraulic response including sluggish boom, arm, or bucket movements despite normal engine RPM
• Intermittent loss of auxiliary hydraulic functions such as breaker or grapple operation
• Engine automatically derating to low idle or entering limp mode during operation
• Diagnostic monitor displaying communication fault messages when accessed through the cab display

Potential Causes

The most common technical causes for DWJ0KA on used PC110-8M0 excavators include:

• Damaged or corroded CAN bus wiring harness between the ECM and HCU, particularly at harness routing points near the swing bearing where flex cables experience constant movement
• Loose or corroded electrical connectors at either the ECM (located near the battery box) or HCU (mounted on the main control valve)
• Failed termination resistors on the CAN bus network causing signal reflection and data corruption
• ECM or HCU internal circuit board failure due to moisture intrusion or voltage spikes from jump-starting
• Deteriorated harness insulation from engine heat exposure, especially on machines with 5,000+ operating hours

How to Troubleshoot and Fix Code DWJ0KA

Step 1: Initial Diagnostic Scan Connect a Komatsu diagnostic software tool (KOMTRAX or equivalent) to retrieve active and pending codes. Document all fault codes and freeze frame data. Clear codes and attempt to replicate the fault during normal operation to determine if the issue is intermittent or constant.

Step 2: Visual Harness Inspection Thoroughly inspect the CAN bus wiring harness from ECM to HCU. On used excavators, pay special attention to harness sections routed along the upper structure where continuous swing motion causes abrasion. Look for chafed wire insulation, green corrosion on copper strands, or previous repair attempts with electrical tape.

Step 3: Connector and Pin Testing Disconnect both ECM and HCU connectors. Inspect pins for corrosion, bent contacts, or moisture. Using a digital multimeter, measure CAN High and CAN Low wire resistance (should read 60 ohms between CAN-H and CAN-L with termination resistors intact). Check for short circuits to ground (should read infinite resistance).

Step 4: Voltage and Signal Verification With ignition on and connectors attached, back-probe the CAN bus wires at the ECM connector. CAN-High should measure approximately 2.5-3.5 volts DC, while CAN-Low should read 1.5-2.5 volts DC at rest. Fluctuating or absent voltage indicates communication failure.

Step 5: Component Replacement Protocol If harness and connections test properly, suspect control module failure. For used machines, the HCU fails more frequently than the ECM. Replace the suspected module with a known-good unit and recalibrate using Komatsu diagnostic software. Always update ECM/HCU firmware to the latest version to resolve known communication bugs.

Critical for Used Equipment: Before replacing expensive control modules, thoroughly clean all ground points on the chassis and engine block. Poor grounding causes 30-40% of communication faults on high-hour machines.

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Disclaimer: This guide provides general troubleshooting procedures. Always consult the Komatsu PC110-8M0 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may void warranties or cause additional equipment damage.