What is Komatsu PC110-8M0 Fault Code DA25KP?

Fault Code DA25KP indicates a DEF (Diesel Exhaust Fluid) pump system malfunction or communication error in the Komatsu PC110-8M0's aftertreatment system. This code specifically relates to the selective catalytic reduction (SCR) system's inability to properly deliver or monitor DEF flow to reduce NOx emissions. The DEF pump controller either cannot communicate with the main engine control module (ECM), or the pump itself has failed to meet operational parameters.

This is critical for the PC110-8M0 because Komatsu's Tier 4 Final emissions compliance depends on proper SCR operation. When this code activates, the machine may enter derate mode to prevent emissions violations, significantly impacting jobsite productivity. For used excavator owners, this fault often signals wear in the DEF delivery system components, which are particularly vulnerable to contamination and electrical corrosion over time.

Common Symptoms

• Amber or red warning light illuminated on the instrument cluster, often accompanied by a DEF system icon
• Engine power derate progressing from 25% to 50% reduction if the fault persists beyond predetermined time limits
• DEF gauge reading inaccurately or showing empty despite adequate fluid levels
• Rough idle or hesitation during operation, particularly under load
• Audible alarm or repeated warning chimes when starting the machine or after extended runtime

Potential Causes

The most common technical reasons for DA25KP on used PC110-8M0 excavators include:

• DEF pump electrical connector corrosion – particularly at the 12-pin harness connection behind the left side panel, where moisture intrusion is common
• Failed DEF pump motor or internal pressure sensor due to crystallized urea buildup from contaminated or old DEF
• Damaged wiring harness at known rub points near the doser unit mounting bracket
• ECM communication bus failure on the CAN line between the DEF control unit and main controller
• Low system voltage from aging batteries or failing alternators, preventing pump initialization
• Contaminated DEF fluid causing pump cavitation or sensor fouling (common in machines with unknown service history)

How to Troubleshoot and Fix Code DA25KP

Step 1: Verify DEF Quality and Level Check that the DEF tank contains fresh fluid (less than 12 months old) meeting ISO 22241 standards. Drain and replace if contamination is suspected. For used excavators, old DEF crystallizes and causes pump failure, so always start here before electrical diagnostics.

Step 2: Inspect Electrical Connections Using a multimeter, check for 12V power supply at the DEF pump connector (typically pins 1 and 12). Inspect the wiring harness from the pump to the ECM for chafing, especially where it routes near the engine mount. On used machines, connector corrosion is extremely common—clean contacts with electrical contact cleaner and apply dielectric grease.

Step 3: Test DEF Pump Operation Connect Komatsu diagnostic software (KOMTRAX Plus or PC-compatible diagnostic tool) to command the DEF pump manually. Listen for pump motor activation. If no sound occurs and voltage is present, the pump motor has likely failed. Measure resistance across pump terminals (should be 3-6 ohms typically).

Step 4: Check CAN Bus Communication Verify CAN High and CAN Low signals at the DEF control module using an oscilloscope or advanced multimeter. Look for 2.5V baseline with proper signal fluctuation. Damaged CAN wiring will show no communication or erratic voltage.

Step 5: Inspect for Mechanical Issues Remove the DEF doser unit and check for crystallization around the injector nozzle. On high-hour used excavators, this often requires complete doser replacement rather than just pump service.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and seek qualified diesel technician assistance for complex electrical diagnostics or emissions system repairs.