What is Komatsu PC220-10 Fault Code L03CA351?

Fault Code L03CA351 indicates a malfunction in the Diesel Particulate Filter (DPF) differential pressure sensor circuit on the Komatsu PC220-10 excavator. This code triggers when the Engine Control Module (ECM) detects an abnormal voltage or signal from the sensor that monitors exhaust backpressure across the DPF.

The differential pressure sensor measures the pressure difference between the inlet and outlet of the DPF, allowing the ECM to determine soot accumulation levels and initiate regeneration cycles when necessary. On the PC220-10 equipped with Komatsu's SAA6D107E-3 engine and Tier 4 Final emissions system, this sensor is critical for maintaining emissions compliance and preventing engine derate. A faulty sensor or circuit prevents proper DPF regeneration management, potentially leading to excessive soot buildup, reduced engine performance, and increased fuel consumption.

Common Symptoms

• Engine warning light illuminated on the instrument cluster with reduced engine power
• Automatic regeneration cycles failing to initiate or complete properly
• Engine derate mode activated, limiting maximum RPM to approximately 1,800-2,000 RPM
• Increased exhaust smoke (black or gray) during normal operation
• DPF pressure gauge reading abnormally high or showing no response to load changes

Potential Causes

The most frequent causes of L03CA351 on used PC220-10 excavators include:

• Damaged or corroded wiring harness at the sensor connector, especially where the harness routes near the turbocharger and exhaust manifold (known rub point on this model)
• Failed differential pressure sensor due to heat stress or internal electrical component degradation
• Blocked sensing tubes connecting the sensor to the DPF housing, clogged with carbon deposits or water intrusion
• ECM connector pin corrosion affecting sensor ground or signal circuits
• Broken or disconnected sensing hoses from vibration or previous maintenance work

How to Troubleshoot and Fix Code L03CA351

Step 1: Visual Inspection Begin by inspecting the differential pressure sensor located on the right side of the engine, near the DPF canister. Check all wiring harness connections for corrosion, damaged pins, or oil contamination. On used excavators, examine where the harness passes over the exhaust components for signs of heat damage or abrasion—this is a common failure point.

Step 2: Check Sensing Lines Disconnect the rubber sensing tubes from the sensor and inspect for blockages. Blow compressed air (maximum 30 PSI) through both lines to verify they're clear. Check for cracks or disconnections in the tubing running to the DPF inlet and outlet ports.

Step 3: Electrical Testing Using a digital multimeter, measure the sensor supply voltage at the connector (should read approximately 5.0V with ignition on). Test sensor signal output voltage—it should vary between 0.5V and 4.5V depending on pressure. Check ground circuit continuity to the ECM (should be less than 1 ohm resistance).

Step 4: Component Testing If wiring checks pass, test the sensor itself using Komatsu KOMTRAX diagnostic software or compatible scan tool to read live sensor data. Compare pressure readings at idle versus high idle—values should change proportionally. For used machines, corrosion inside the sensor housing often causes intermittent failures not detected by static testing.

Step 5: Repair or Replace Replace damaged connectors or repair harness chafing with high-temperature electrical tape and protective loom. If the sensor fails testing, replace with genuine Komatsu part number 6754-81-7110 or equivalent. After repairs, clear the fault code and perform a forced regeneration cycle to verify proper operation.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific machine serial number, and consider professional diagnosis for complex electrical issues or if warranty coverage applies.