Komatsu PC60-8 Fault Code CA351: Complete Diagnostic Guide

What is Komatsu PC60-8 Fault Code CA351?

Fault Code CA351 indicates a communication error between the Engine Control Module (ECM) and the Hydraulic Control Module (HCM) on the Komatsu PC60-8 excavator. This code specifically signals that the CAN (Controller Area Network) bus communication link has been interrupted or is experiencing data transmission failures between these two critical control systems.

The ECM manages engine performance and emissions, while the HCM controls hydraulic functions including pump output and flow distribution. When these modules cannot communicate properly, the excavator's integrated control system cannot optimize performance or coordinate engine speed with hydraulic demand. This is particularly critical on the PC60-8, which relies on electronic communication for its advanced load-sensing hydraulic system and fuel efficiency features.

Common Symptoms

• Warning lamp illuminated on the instrument panel, often accompanied by reduced machine responsiveness
• Sluggish hydraulic performance or inconsistent boom/arm/bucket speeds due to improper engine-hydraulic coordination
• Engine may not respond to throttle inputs correctly or fail to automatically adjust RPM based on hydraulic load
• Intermittent loss of auxiliary functions including pattern change valve or attachment controls
• Machine may enter derate mode, limiting engine power to protect components from uncoordinated operation

Potential Causes

The most common technical causes for CA351 on used PC60-8 excavators include:

• CAN bus wiring harness damage from rubbing against the frame near the engine mount area or along the right-side chassis rail (known wear point on this model)
• Corroded or loose connector pins at the ECM or HCM connection points, especially on machines with high hour counts or exposure to moisture
• Failed termination resistor in the CAN network causing signal reflection and data corruption
• ECM or HCM internal failure, though less common than wiring issues in used equipment
• Voltage supply problems to either control module due to aging main harness or poor ground connections

How to Troubleshoot and Fix Code CA351

Step 1: Visual Inspection Begin by inspecting the wiring harness between the ECM (located behind the operator's seat) and HCM (mounted near the hydraulic pump). Look for chafing, cuts, or pinch points, particularly where harnesses pass through bulkheads. On used excavators, check for previous repair attempts using electrical tape, which often indicates recurring issues.

Step 2: Connector Examination Disconnect and inspect all CAN bus connectors at both modules. Clean connector pins with electrical contact cleaner and check for bent pins, corrosion (green/white deposits), or moisture intrusion. Verify connector lock mechanisms are intact—worn connectors are common on older machines.

Step 3: Electrical Testing Using a digital multimeter, measure CAN-High and CAN-Low voltage at the ECM connector with ignition on, engine off. You should read approximately 2.5V on each line at rest. Check for 120-ohm resistance between CAN-High and CAN-Low with modules disconnected, confirming termination resistors are functional.

Step 4: Diagnostic Software Analysis Connect Komatsu KOMTRAX or compatible diagnostic software to read real-time CAN bus traffic and identify which module is failing to transmit. This pinpoints whether the ECM or HCM is the source of communication failure.

Step 5: Harness Continuity Check Test continuity of CAN-High and CAN-Low wires from ECM to HCM. On used machines, internal wire breaks can occur without visible external damage due to vibration fatigue.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues or if you lack proper diagnostic equipment.