Komatsu PC360-7 Fault Code DA20KT: Complete Diagnostic Guide

What is Komatsu PC360-7 Fault Code DA20KT?

Fault Code DA20KT indicates a communication error between the Engine Controller (ECM) and the Pump Controller (PMC) in the Komatsu PC360-7 excavator. This code specifically points to a CAN bus communication failure or data transmission interruption between these two critical control modules.

The PC360-7 relies on continuous data exchange between the ECM and PMC to optimize hydraulic pump output based on engine load and operator demand. When communication breaks down, the machine cannot properly coordinate engine speed with hydraulic pump displacement, leading to reduced efficiency and potential performance limitations. This fault is particularly critical because the PC360-7's advanced CLSS (Closed-Center Load Sensing System) depends on seamless controller communication to deliver its fuel-saving benefits.

Common Symptoms

When fault code DA20KT is active, operators typically experience:

• Warning light activation on the monitor panel with reduced machine performance notification
• Loss of power mode functionality – inability to switch between work modes (H, S, L, or B modes)
• Sluggish hydraulic response or inconsistent boom/arm/bucket speed despite normal engine RPM
• Fuel consumption increase due to inability to match pump output to actual load requirements
• Engine derating or limiting to maximum 1,800 RPM in severe cases to protect drivetrain components

Potential Causes

The most common technical causes for DA20KT on used PC360-7 excavators include:

• CAN bus wiring harness damage – particularly at the bend point near the operator's cab where the harness routes to the engine compartment (known wear location)
• Corroded or loose connector terminals on the 18-pin ECM connector (C1) or 16-pin PMC connector (P1)
• Failed termination resistor in the CAN communication circuit (120-ohm resistor failure)
• Water intrusion into controller housings from damaged seals or improper washing procedures
• ECM or PMC internal failure – more common in machines exceeding 8,000 operating hours
• Voltage supply issues providing inadequate power (below 22V) to either controller during cranking

How to Troubleshoot and Fix Code DA20KT

Step 1: Visual Inspection and Connector Check

Begin by thoroughly inspecting the wiring harness between the engine compartment and the main valve area. On used PC360-7 machines, focus on the harness routing point approximately 12 inches behind the cab where the bundle flexes during swing operation—this is a notorious rub point. Check all connector pins on both the ECM (located on left side of engine) and PMC (mounted on main control valve) for:

• Green corrosion or oxidation on terminals
• Bent or pushed-back pins preventing proper contact
• Moisture inside connector boots

Clean all connections with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: CAN Bus Resistance Testing

Using a digital multimeter, disconnect both controllers and measure resistance between CAN-H and CAN-L terminals. You should read approximately 60 ohms (two 120-ohm termination resistors in parallel). A reading of 120 ohms indicates one failed termination resistor; infinite resistance suggests complete circuit break. Check continuity of both CAN-H and CAN-L wires individually from ECM to PMC—any open circuit requires harness repair or replacement.

Step 3: Voltage Supply Verification

With controllers reconnected, measure battery voltage at both the ECM and PMC power supply pins during engine cranking. Voltage should not drop below 22V. Lower readings indicate battery degradation, poor ground connections, or excessive starter draw common in high-hour used machines. Inspect the main ground strap between engine block and frame—corrosion here causes numerous electrical faults.

Step 4: Advanced Diagnostics with Komatsu KTEP Software

If physical inspection reveals no issues, connect Komatsu KTEP (Komatsu Technician Expert Program) diagnostic software via the service port under the operator seat. Monitor live CAN bus traffic between controllers. Intermittent communication (packet loss) visible in the data stream typically indicates a marginal connector or internal harness break that only fails under vibration. For used excavators, replacing suspect harnesses preemptively often proves more cost-effective than repeated diagnostics.

---

Disclaimer: This guide provides general diagnostic direction for experienced technicians. Always consult the official Komatsu PC360-7 Shop Manual and follow lockout/tagout procedures. For complex electrical issues or controller replacement, seek certified Komatsu dealer support to ensure proper programming and calibration.