Komatsu PC800-8R Fault Code DGH2KB: Complete Diagnostic Guide

What is Komatsu PC800-8R Fault Code DGH2KB?

Fault Code DGH2KB indicates a communication error or data link failure between the engine controller (ECM) and the hydraulic system controller on the Komatsu PC800-8R excavator. This code specifically relates to the CAN bus communication network that allows critical machine systems to exchange operational data in real-time.

The PC800-8R relies on continuous communication between its Engine Control Module (ECM) and Pump Control Unit (PCU) to optimize fuel efficiency, hydraulic performance, and emissions control. When this data link is interrupted or corrupted, the machine cannot properly coordinate engine output with hydraulic demand, leading to reduced performance and potential component protection modes. This is particularly critical on the PC800-8R's advanced KOMTRAX-equipped systems, where multiple controllers must work in harmony.

Common Symptoms

When DGH2KB is active, operators typically experience:

• Warning light illumination on the monitor panel, often accompanied by a communication error message
• Reduced hydraulic response or sluggish boom/arm movements due to the system entering a failsafe mode
• Engine power derate, limiting RPM to protect components when proper load data cannot be communicated
• Intermittent loss of monitor display functions, including fuel consumption data or system temperatures
• Multiple secondary fault codes appearing simultaneously as various systems lose communication

Potential Causes

The most common technical causes for DGH2KB on used PC800-8R excavators include:

• CAN bus wiring harness damage at known rub points near the engine mounting brackets or along the right-hand chassis rail
• Corroded or moisture-contaminated connectors at the ECM or PCU, particularly the 38-pin main harness connector
• Failed termination resistors within the CAN network (120-ohm resistors at network endpoints)
• ECM or PCU internal failure, though less common than wiring issues on used machines
• Voltage supply problems to controllers due to aging battery cables or poor grounding points
• Aftermarket component interference from non-OEM monitors or tracking devices improperly connected to the CAN network

How to Troubleshoot and Fix Code DGH2KB

Step 1: Visual Inspection Begin with a thorough physical inspection of all wiring harnesses between the engine bay and operator cab. On used excavators, focus on areas where harnesses pass through bulkheads or near moving components. Look for chafed insulation, pinched wires, or evidence of previous repairs. Inspect all connector pins for corrosion, bent terminals, or moisture intrusion—particularly the large connectors at the ECM and PCU.

Step 2: Electrical Testing Using a digital multimeter, verify proper voltage supply to both the ECM and PCU (typically 24V on this model). Check ground connections at the engine block and frame rails for resistance below 0.5 ohms. With Komatsu diagnostic software (KTEC or compatible scan tool), monitor live CAN bus communication. Check for proper termination resistance by measuring between CAN-High and CAN-Low pins at disconnected controller connectors—you should read approximately 60 ohms with both terminators in place.

Step 3: Component Isolation If wiring tests pass, systematically disconnect non-essential CAN bus devices (aftermarket displays, telematics units) to identify potential interference sources. For used excavators with unknown service history, consider that previous technicians may have installed splices or taps that create signal reflections. Replace any suspect connectors before condemning controllers, as connector terminal tension loss is common on high-hour machines.

Step 4: Controller Verification If all wiring and connections test properly, the fault likely resides in either the ECM or PCU. Cross-reference with Komatsu service bulletins for your machine's serial number range, as certain production batches had known controller software issues requiring updates. Controller replacement should be a last resort after exhausting all wiring and connection possibilities.

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Disclaimer: This guide provides general diagnostic information for experienced technicians. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnostic assistance for complex electrical issues. Improper troubleshooting can cause additional system damage.