What is Komatsu PC110-8M0 Fault Code DAF8KB?

Fault Code DAF8KB indicates a communication error between the Engine Control Module (ECM) and the Machine Controller on the Komatsu PC110-8M0 excavator. This diagnostic trouble code specifically signals that the CAN (Controller Area Network) bus communication between these two critical control systems has been interrupted or degraded beyond acceptable parameters.

This code is particularly critical for the PC110-8M0 because the ECM and Machine Controller must continuously exchange data to coordinate engine performance with hydraulic demand, emissions controls, and operator inputs. When communication fails, the excavator cannot properly manage fuel injection timing, throttle response, or implement safety protocols, potentially leading to reduced machine performance or complete operational shutdown.

Common Symptoms

• Warning lamp illumination on the instrument cluster, often accompanied by a machine derate mode limiting engine RPM to 1,500 or lower
• Erratic throttle response or failure of the engine to respond properly to joystick/pedal inputs
• Hydraulic system underperformance, with sluggish boom, arm, or swing functions due to improper engine-hydraulic coordination
• Intermittent engine shutdown or failure to start, especially after the machine has been operating and components are warm
• Multiple secondary fault codes appearing simultaneously as dependent systems lose communication synchronization

Potential Causes

The DAF8KB code on used PC110-8M0 excavators typically stems from these technical failures:

• CAN bus wiring harness damage at known rub points near the upper swivel bearing and along the right-hand chassis rail where harnesses flex during swing operation
• Corroded or moisture-infiltrated connectors at the ECM (located behind the operator's seat) or Machine Controller (mounted under the right console)
• Failed termination resistors within the CAN network, commonly 120-ohm resistors that degrade over time in high-vibration environments
• ECM or Machine Controller internal failure, particularly in machines with over 6,000 operating hours where capacitor degradation affects signal processing
• Voltage supply issues from the main power harness, causing insufficient power to maintain stable CAN communications (typically requires 9-16V DC)

How to Troubleshoot and Fix Code DAF8KB

Step 1: Visual Harness Inspection Begin by thoroughly inspecting the main wiring harness routing between the ECM and Machine Controller. On used excavators, focus on areas where the harness passes through the swivel joint and near hydraulic hoses. Look for abrasion marks, exposed copper, or heat damage. Check all connector pins for corrosion, bent contacts, or moisture intrusion using a flashlight and magnifying glass.

Step 2: CAN Bus Electrical Testing Using a digital multimeter, measure CAN-High and CAN-Low voltage at the ECM connector (typically pins 23 and 24). With ignition on and engine off, you should read approximately 2.5V on each line. Measure resistance between CAN-High and CAN-Low; a properly terminated network shows 60 ohms (two 120-ohm resistors in parallel). Values outside 55-65 ohms indicate termination resistor failure or wiring faults.

Step 3: Software Diagnostics and Component Testing Connect Komatsu KPIM diagnostic software to the service port under the operator console. Monitor live CAN bus traffic and error frame counts. Excessive error frames (>50 per minute) indicate signal integrity problems. If wiring tests pass, substitute-test the Machine Controller first (more common failure point), then the ECM if necessary. For used machines, always clean all connector contacts with electrical contact cleaner and apply dielectric grease before reassembly to prevent future corrosion-related communication failures.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and seek professional assistance from certified Komatsu technicians for complex electrical diagnostics and repairs.