What is Kobelco SK140LC-8 Fault Code A235?

Fault Code A235 on the Kobelco SK140LC-8 excavator indicates a malfunction in the pilot pump pressure sensor circuit. This code triggers when the Electronic Control Unit (ECU) detects an abnormal voltage signal or complete loss of communication from the pilot pressure sensor, which monitors hydraulic pressure in the pilot control system.

The pilot pump pressure sensor plays a critical role in the SK140LC-8's hydraulic control architecture. This sensor provides real-time pressure data to the ECU, enabling precise control of joystick inputs and ensuring smooth, proportional operation of hydraulic functions. When this sensor circuit fails, the machine's ability to regulate hydraulic performance is compromised, potentially leading to erratic operation or complete loss of pilot controls. For used excavators, this code often surfaces due to sensor degradation, wiring damage from engine vibration, or corrosion in electrical connectors exposed to moisture over years of operation.

Common Symptoms

When Code A235 is active, operators typically experience:

• Erratic or unresponsive joystick controls with delayed or inconsistent hydraulic response
• Warning light illumination on the instrument cluster, often accompanied by audible alarms
• Loss of fine control during precision work, with hydraulic functions responding in an all-or-nothing manner
• Reduced hydraulic performance or complete inability to execute combined functions
• Machine entering limp mode where all hydraulic operations are restricted to protect the system

Potential Causes

The most common technical failures triggering A235 on used SK140LC-8 excavators include:

• Faulty pilot pump pressure sensor due to internal component wear or diaphragm failure
• Damaged or chafed wiring harness between the sensor and ECU, particularly at routing points near the pump or along the chassis rail where vibration causes wire insulation breakdown
• Corroded or loose electrical connectors at the sensor plug or ECU terminals, especially on machines operated in high-moisture environments
• Short circuit to ground caused by harness contact with metal surfaces or pinched wires during previous repairs
• ECU power supply issues affecting the sensor's reference voltage (typically 5V)
• Contaminated hydraulic oil causing sensor membrane degradation or blockage

How to Troubleshoot and Fix Code A235

Step 1: Visual Inspection and Connector Examination Begin by locating the pilot pump pressure sensor on the pilot pump assembly. Disconnect the electrical connector and thoroughly inspect both the sensor pins and harness terminals for corrosion, bent pins, or moisture intrusion. On used excavators, apply electrical contact cleaner and verify the connector locking mechanism functions properly. Check the wiring harness routing for obvious damage, particularly where it contacts engine components or frame edges.

Step 2: Electrical Testing with Diagnostic Tools Using a digital multimeter, measure the sensor's supply voltage at the harness connector with the ignition on. You should see approximately 5 volts DC on the reference wire. Next, check for continuity on the ground circuit—it should read near 0 ohms to chassis ground. Test the signal wire resistance; specifications typically range between 200-500 ohms depending on operating pressure, but consult the service manual for exact values. If voltage or ground circuits fail, trace the harness back toward the ECU, checking for breaks or shorts.

Step 3: Sensor Function and Replacement If electrical tests pass, perform a functional pressure test using Kobelco diagnostic software (if available) or a mechanical pressure gauge connected to the pilot circuit. Compare actual hydraulic pressure readings with sensor output voltage—the signal should increase proportionally with pressure. For used machines, even if readings appear borderline acceptable, consider sensor replacement if the unit is original, as internal drift is common after 5,000+ operating hours. After replacing the sensor or repairing wiring, clear the fault code using diagnostic software and cycle the machine through all hydraulic functions to verify proper operation.

Critical Note for Used Equipment: Before ordering expensive replacement sensors, always check for harness wear at flex points near the pilot pump and main valve area. On older SK140LC-8 models, repeated vibration commonly causes wire fatigue failures that mimic sensor malfunctions.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Kobelco service manual for your specific machine serial number and consider professional diagnostics for complex electrical issues. Improper repairs may void warranties or cause additional damage.