What is Kobelco SK350-6E Fault Code D-2?

Kobelco SK350-6E Fault Code D-2 indicates a malfunction in the hydraulic pump control system, specifically related to the main pump solenoid valve circuit or its feedback signal. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an abnormal voltage, open circuit, or short circuit in the proportional solenoid valve that regulates hydraulic pump displacement.

This code is critical for the SK350-6E because the pump control solenoid directly affects hydraulic flow and system pressure. When this circuit malfunctions, the excavator loses its ability to properly modulate hydraulic power distribution across all functions, leading to significant performance degradation and potential component damage from improper pressure regulation.

Common Symptoms

When Code D-2 is active on your Kobelco SK350-6E, operators typically experience:

• Hydraulic system operating at reduced power or fixed displacement mode, resulting in sluggish boom, arm, and bucket movements
• Warning light illumination on the instrument cluster with possible audible alarm
• Erratic hydraulic response where functions may surge or respond inconsistently to joystick inputs
• Increased fuel consumption due to the pump running at non-optimized settings
• Overheating of hydraulic oil caused by improper flow regulation

Potential Causes

Code D-2 on used SK350-6E excavators most commonly results from:

• Worn or failed pump control solenoid valve (internally shorted coil or mechanical valve sticking)
• Damaged wiring harness between the ECM and solenoid, particularly where the harness runs along the pump housing (known wear point)
• Corroded or loose connector pins at the solenoid connection (common in machines with 5,000+ operating hours)
• ECM internal fault in the pump control driver circuit (less common but possible in high-hour machines)
• Low voltage supply to the solenoid due to poor ground connections or aged battery cables
• Contaminated hydraulic fluid causing mechanical binding of the solenoid spool

How to Troubleshoot and Fix Code D-2

Step 1: Visual Inspection and Code Verification Using Kobelco diagnostic software (ITMS) or a compatible scan tool, verify Code D-2 is current and not historical. Inspect the pump solenoid connector and wiring harness for obvious damage, oil contamination, corrosion, or signs of rubbing against the pump housing—a frequent issue on used SK350-6E models.

Step 2: Electrical Testing Disconnect the solenoid connector and measure resistance across the solenoid coil terminals using a digital multimeter. The specification should be approximately 8-12 ohms at room temperature (verify with service manual). Check for voltage supply from the ECM with the key on—should read approximately 12V DC. Inspect ground circuit continuity using resistance measurement to chassis ground (should be less than 1 ohm).

Step 3: Component Testing and Harness Verification With power disconnected, carefully inspect the wiring harness routing for areas where previous repairs, chafing against brackets, or heat damage may have occurred. On used excavators, pay special attention to connector pin tension and any signs of moisture intrusion. If electrical tests pass, the solenoid valve itself may be mechanically stuck—consider removing and bench-testing or replacing the unit with an OEM or quality aftermarket solenoid.

Step 4: System Verification After repairs, clear the fault code using diagnostic software, operate the machine through all hydraulic functions, and verify Code D-2 does not return. Monitor hydraulic oil temperature and system response during a work cycle to ensure proper pump modulation has been restored.

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Disclaimer: This guide provides general troubleshooting information for Kobelco SK350-6E Code D-2. Always consult the official Kobelco service manual for your specific machine serial number and consult with a certified heavy equipment technician for complex electrical diagnostics or hydraulic system repairs.