What is Komatsu PC200-10 Fault Code DWA2KB?

Fault Code DWA2KB indicates a DEF (Diesel Exhaust Fluid) Pump Relay Circuit Malfunction in the Komatsu PC200-10 excavator's aftertreatment system. This diagnostic trouble code specifically relates to the electrical circuit controlling the DEF pump relay, which is responsible for activating the pump that delivers urea solution into the Selective Catalytic Reduction (SCR) system.

This code is critical for the PC200-10 because the machine relies on proper DEF delivery to meet Tier 4 Final emissions standards. When the Electronic Control Module (ECM) detects abnormal voltage, current draw, or circuit continuity in the relay circuit, it triggers DWA2KB. For used excavators, this fault can lead to progressive engine derates and eventual shutdown if not addressed, directly impacting jobsite productivity and compliance with emission regulations.

Common Symptoms

• Amber or red DEF warning light illuminated on the instrument cluster
• Engine power derate after a countdown period (typically starting at 50% power reduction)
• DEF pump failure to activate during refueling or system purge cycles
• Machine may enter induced engine derate mode preventing operation above idle after repeated ignition cycles
• Stored fault code visible through the monitor display or diagnostic software

Potential Causes

The DWA2KB code in used Komatsu PC200-10 excavators typically stems from these technical failures:

• Relay coil failure due to heat cycling and age-related degradation in the engine compartment
• Corroded or loose connector pins at the DEF pump relay socket (common on machines operating in wet or corrosive environments)
• Damaged wiring harness between the ECM and relay, especially at known rub points near the DEF tank mounting bracket
• Failed DEF pump motor creating excessive current draw that damages the relay contacts
• ECM internal relay driver circuit failure (less common but possible in high-hour machines)
• Water intrusion into the relay junction box causing short circuits or corrosion

How to Troubleshoot and Fix Code DWA2KB

Step 1: Visual Inspection Locate the DEF pump relay in the main relay box (typically near the battery compartment). Inspect all connectors and terminals for corrosion, bent pins, or moisture. On used excavators, check the wiring harness routing from the relay to the DEF pump for chafing against frame members or heat shields.

Step 2: Electrical Testing Using a digital multimeter, check relay coil resistance (typically 70-90 ohms across coil terminals). With the key on and engine off, measure voltage supply to the relay (should show battery voltage). Check for ground continuity on the control circuit from the ECM. Use Komatsu KOMTRAX diagnostic software to command the relay on/off and monitor actual vs. commanded states.

Step 3: Component Testing Remove the relay and bench-test it by applying 12V across coil terminals while checking continuity across normally-open contacts. If the relay fails to close, replace it with a genuine Komatsu relay (part-specific to avoid amperage mismatch). Before reinstalling, clean all connector terminals with electrical contact cleaner and apply dielectric grease to prevent future corrosion.

Step 4: DEF Pump Verification After relay replacement, test DEF pump current draw using an ammeter (normal draw: 8-12 amps during operation). Excessive amperage indicates pump motor failure requiring replacement. Clear codes using diagnostic software and perform a DEF system purge cycle to verify proper operation.

For used excavators, always inspect harness strain relief points and secure any loose wiring before completing repairs. Check the DEF tank heater circuit as well, since shared ground circuits can cause phantom relay faults.

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Disclaimer: This guide provides general troubleshooting information for the Komatsu PC200-10. Always consult the manufacturer's service manual and qualified technicians for machine-specific repairs. Improper diagnostics can cause additional system damage or safety hazards.