What is Kobelco SK135SR-2 Fault Code R134?

Kobelco SK135SR-2 Fault Code R134 indicates a hydraulic pump pressure sensor circuit malfunction in the main hydraulic system. This code is triggered when the Electronic Control Module (ECM) detects abnormal voltage readings or an open/short circuit from the pump pressure sensor, which monitors the main hydraulic pump's output pressure. This sensor is critical for the SK135SR-2's Load Sensing System, as it allows the ECM to optimize engine output based on hydraulic demand, ensuring fuel efficiency and preventing pump over-pressurization. When this code activates, the machine may enter a protective derate mode, reducing hydraulic performance to prevent potential pump or circuit damage.

Common Symptoms

• Reduced hydraulic power across all functions (boom, arm, bucket, and swing movements become noticeably slower)
• Warning light illuminated on the instrument cluster, often accompanied by an audible alarm
• Engine automatically derates to lower RPM, limiting overall machine performance
• Intermittent hydraulic response, where functions work normally at times but suddenly lose power
• Error code R134 displayed on the monitor panel or retrieved via diagnostic software

Potential Causes

The most common causes of Code R134 on used Kobelco SK135SR-2 excavators include:

• Failed hydraulic pump pressure sensor due to internal component wear or contamination from hydraulic fluid breakdown
• Damaged or corroded wiring harness connecting the sensor to the ECM, particularly at known rub points near the pump mounting area and along the main chassis harness
• Connector corrosion or moisture intrusion at the sensor plug, common in machines operating in wet or coastal environments
• Poor electrical ground connection at the sensor mounting bracket or ECM ground points
• ECM internal fault (less common) affecting the sensor input circuit
• Hydraulic fluid contamination causing sensor membrane damage or erratic readings

How to Troubleshoot and Fix Code R134

Step 1: Visual Inspection Begin by inspecting the hydraulic pump pressure sensor located on the main pump assembly. Check for physical damage, oil leaks, or loose mounting. Examine the wiring harness from the sensor to the ECM, paying special attention to areas where the harness contacts the frame or pump housing—common wear points on used SK135SR-2 models.

Step 2: Electrical Testing Disconnect the sensor connector and use a multimeter to check for 5-volt reference voltage from the ECM at the connector (ignition on, engine off). Then measure the sensor's internal resistance, which should typically read between 200-500 ohms (consult service manual for exact specifications). Check for continuity in all wires between the sensor and ECM, and verify ground integrity at the sensor mounting point.

Step 3: Advanced Diagnostics Connect Kobelco diagnostic software (or compatible heavy equipment scanner) to monitor live sensor data. Compare the pressure sensor readings at idle and under load against manufacturer specifications. On used excavators, clean all connector pins with electrical contact cleaner and apply dielectric grease to prevent future corrosion—a critical maintenance step often overlooked.

Step 4: Component Replacement If testing confirms sensor failure, replace the pump pressure sensor with a genuine Kobelco or high-quality OEM equivalent part. After installation, clear the fault code and perform a system calibration using diagnostic software. If the harness shows damage, repair or replace the affected section, ensuring proper routing away from heat and friction points.

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Disclaimer: This guide provides general troubleshooting information for Kobelco SK135SR-2 Fault Code R134. Hydraulic and electrical system diagnostics require proper training and equipment. Always consult the manufacturer's service manual and consider professional assistance from a certified Kobelco technician for complex repairs, especially on used machinery where multiple underlying issues may exist.