What is Kobelco SK250-6E Fault Code A-2?

Fault Code A-2 on the Kobelco SK250-6E indicates a hydraulic pump discharge pressure sensor circuit malfunction. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage signal from the main pump pressure sensor, typically reading outside the normal operating range of 0.5-4.5 volts.

The hydraulic pump discharge pressure sensor is critical for the SK250-6E's advanced load-sensing hydraulic system. This sensor continuously monitors the discharge pressure from the main hydraulic pumps and sends real-time data to the ECM, which then optimizes pump flow and engine output for maximum fuel efficiency and performance. When this sensor circuit fails, the excavator loses its ability to properly regulate hydraulic power, potentially causing reduced productivity and increased fuel consumption.

Common Symptoms

When Code A-2 is active on your Kobelco SK250-6E, operators typically experience:

• Illuminated warning light on the instrument cluster, often accompanied by an audible alarm
• Reduced hydraulic power across all functions (boom, arm, bucket, and swing)
• Engine automatically derating to a lower RPM to protect the hydraulic system
• Sluggish response during combined operations (multi-function work)
• Inconsistent cycle times even when the throttle is at maximum position

Potential Causes

The A-2 fault code on used SK250-6E excavators commonly stems from:

• Pressure sensor failure due to internal component degradation or contaminated hydraulic oil exposure
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the main pump assembly and along the boom base
• Corroded or loose connector pins at the sensor plug or ECM interface (common on machines with 5,000+ operating hours)
• ECM voltage supply issues providing incorrect reference voltage to the sensor circuit
• Contaminated hydraulic oil causing sensor diaphragm fouling or internal failure
• Previous collision damage to the pump area affecting sensor mounting or calibration

How to Troubleshoot and Fix Code A-2

Step 1: Visual Inspection Begin by thoroughly inspecting the hydraulic pump pressure sensor located on the main pump housing. Check for physical damage, oil leaks around the sensor body, and corrosion on the connector. On used excavators, pay special attention to the wiring harness routing from the sensor to the ECM—look for abrasion damage where the harness contacts the pump or frame members.

Step 2: Electrical Testing Disconnect the sensor connector and use a digital multimeter to check the reference voltage from the ECM (should read approximately 5 volts with the key on, engine off). Test the sensor resistance across the signal and ground pins; typical readings should be between 200-400 ohms depending on ambient temperature. Check for continuity on all wires between the sensor and ECM, and verify ground integrity with less than 0.5 ohms resistance.

Step 3: Sensor Output Verification Reconnect the sensor and backprobe the signal wire with the engine running at idle. The sensor should output approximately 0.8-1.2 volts at idle pressure. Increase engine RPM and activate hydraulic functions—voltage should rise proportionally to 3.5-4.2 volts under load. Erratic readings or voltages stuck at 0 or 5 volts indicate sensor failure.

Step 4: Used Equipment Specific Checks For used excavators, inspect the connector terminals for greenish corrosion or bent pins. Apply dielectric grease to prevent future moisture intrusion. Check the hydraulic oil condition—contaminated oil accelerates sensor failure. Verify the sensor mounting torque (typically 15-20 ft-lbs) hasn't loosened from vibration over time.

Step 5: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Kobelco pressure sensor (part number specific to SK250-6E). After installation, use Kobelco diagnostic software or compatible scan tool to clear the code and perform a pressure calibration procedure as outlined in the service manual. Test all hydraulic functions under load to confirm proper operation.

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Disclaimer: This guide provides general troubleshooting information for the Kobelco SK250-6E fault code A-2. Always consult the official Kobelco service manual for your specific machine serial number and operating hour range. If you lack proper diagnostic tools or experience with high-pressure hydraulic systems, consult a certified Kobelco technician to prevent personal injury or further equipment damage.