What is Kobelco SK130-8 Fault Code 6772?

Fault Code 6772 on the Kobelco SK130-8 excavator indicates a "Hydraulic Pump Control System Malfunction" – specifically a communication error or abnormal voltage signal between the Engine Control Module (ECM) and the hydraulic pump control solenoid. This code triggers when the ECM detects an open circuit, short circuit, or out-of-range voltage in the pump control circuit, preventing proper regulation of hydraulic flow and engine load matching.

This fault is critical for the SK130-8 because this model utilizes a sophisticated closed-loop hydraulic system that continuously adjusts pump displacement based on engine load and operator demand. When communication fails, the excavator loses its ability to optimize fuel efficiency and hydraulic performance, potentially causing the machine to operate in a protective derate mode that limits engine RPM and hydraulic output.

Common Symptoms

• Yellow or amber warning light illuminated on the instrument cluster, often accompanied by a "Check Engine" message
• Noticeable loss of hydraulic power during digging, lifting, or slewing operations, particularly under heavy loads
• Engine operating in reduced power mode (derate), limiting maximum RPM to approximately 1,500-1,800 RPM
• Sluggish or erratic hydraulic response when operating multiple functions simultaneously
• Increased fuel consumption due to inability to properly match pump output to engine torque

Potential Causes

The most common technical causes for Code 6772 on used SK130-8 excavators include:

• Damaged wiring harness between the ECM and hydraulic pump solenoid, particularly at the main engine harness junction near the battery box (a known rub point on this model)
• Failed or internally shorted pump control solenoid valve, typically due to contaminated hydraulic fluid damaging the coil windings
• Corroded or loose electrical connectors at the pump control solenoid or ECM, especially on machines operated in marine or high-humidity environments
• ECM internal circuit failure, more common in excavators with over 8,000 operating hours
• Voltage supply issues from the main power relay or damaged ground connections at the engine block mounting point

How to Troubleshoot and Fix Code 6772

Step 1: Initial Visual Inspection Begin by inspecting the wiring harness from the ECM (located under the right-hand console) to the hydraulic pump solenoid valve. Check for chafed wires, particularly where the harness passes through metal brackets near the fuel filter assembly. Inspect all electrical connectors for corrosion, moisture intrusion, or bent pins.

Step 2: Voltage and Resistance Testing Using a digital multimeter, measure voltage at the pump control solenoid connector with the ignition ON (engine not running). You should read approximately 12 volts on the power supply wire. Check solenoid coil resistance – specification is typically 8-15 ohms. Readings below 5 ohms indicate a short; infinite resistance indicates an open circuit requiring solenoid replacement.

Step 3: Signal Circuit Verification Connect Kobelco diagnostic software (Dr.EX or compatible scan tool) to verify real-time signal voltage from the ECM. The control signal should fluctuate between 0.5-4.5 volts during operation. If voltage is fixed at 0V or 5V, suspect ECM internal failure or a severed signal wire.

Step 4: Ground Circuit Testing Verify continuity between the solenoid ground terminal and chassis ground – resistance should be less than 1 ohm. On used excavators, corrosion at ground points mounted to the engine block frequently causes intermittent codes.

Step 5: Component Replacement Priority For used machinery, replace components in this order: (1) solenoid valve (most common failure), (2) damaged harness sections, (3) ECM (least common). Always clear codes and test operation after each replacement.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number and consult qualified hydraulic technicians for complex ECM diagnostics or pump replacement procedures.