What is Kobelco SK140LC-8 Fault Code 20131?

Fault Code 20131 on the Kobelco SK140LC-8 indicates a malfunction in the aftertreatment Diesel Particulate Filter (DPF) differential pressure sensor circuit. This code is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal or communication error from the sensor that monitors pressure differences across the DPF.

The differential pressure sensor plays a critical role in the SK140LC-8's emission control system by measuring the restriction level within the DPF. When this sensor fails or sends faulty data, the ECM cannot accurately determine when regeneration cycles are needed, potentially leading to excessive soot buildup, reduced engine performance, and ultimately catastrophic DPF damage on used machines that may already have accumulated significant operating hours.

Common Symptoms

• DPF warning light illuminated on the instrument cluster, potentially accompanied by a check engine light
• Reduced engine power or derate mode activation, limiting machine performance to protect the aftertreatment system
• Frequent or failed regeneration cycles, with the machine attempting DPF regeneration more often than normal
• Excessive black smoke from the exhaust during operation due to improper regeneration timing
• ECM fault code storage visible through diagnostic software, even if symptoms are intermittent

Potential Causes

The most common technical failures triggering Code 20131 on used SK140LC-8 excavators include:

• Damaged or corroded wiring harness connections at the DPF pressure sensor, particularly where harnesses route near the exhaust system and experience heat cycling
• Failed differential pressure sensor due to carbon buildup on sensing ports or internal electrical component degradation
• Blocked or kinked pressure sensing tubes connecting the sensor to the DPF inlet and outlet measurement points
• ECM software calibration issues or corrupted memory, more common in machines with previous electrical system problems
• Exhaust system leaks near pressure tap points causing inaccurate readings
• Corroded sensor connector pins from moisture intrusion, especially prevalent in machines operated in wet or coastal environments

How to Troubleshoot and Fix Code 20131

Step 1: Visual Inspection Begin by inspecting the DPF differential pressure sensor located on the exhaust aftertreatment assembly. Check all wiring harness connections for corrosion, damaged pins, or loose connections. On used excavators, pay special attention to harness routing near hot exhaust components where insulation may have deteriorated. Inspect the pressure sensing tubes for kinks, blockages, or carbon accumulation at connection points.

Step 2: Electrical Testing Using a digital multimeter, perform voltage and resistance checks on the sensor circuit. With the ignition on and engine off, verify the 5-volt reference supply from the ECM to the sensor. Check sensor ground continuity to ensure less than 1 ohm resistance. Measure the sensor's signal voltage output, which should typically range between 0.5-4.5 volts depending on pressure conditions. Compare readings against Kobelco specifications using KOMTRAX diagnostic software or equivalent dealer-level tools.

Step 3: Component Testing and Replacement If electrical values are within specification, remove the differential pressure sensor and physically inspect the sensing ports for carbon deposits or damage. Clean sensing tubes with compressed air and verify they're not plugged. On used machines with high hours, consider replacing both the sensor and pressure tubes as preventative maintenance, as these components degrade over time. After replacement, clear codes using diagnostic software, perform a manual DPF regeneration cycle, and monitor for code recurrence during operation.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number and seek professional assistance from certified Kobelco technicians for complex diagnostics and repairs involving emission control systems.