What is Hyundai R500LC-7A Fault Code 718-11?

Fault Code 718-11 on the Hyundai R500LC-7A excavator indicates a high voltage condition in the Swing Motor #2 pressure sensor circuit. This diagnostic trouble code (DTC) is triggered when the Electronic Control Unit (ECU) detects an abnormally high voltage signal—typically above 4.8 volts—from the swing motor pressure sensor on the secondary swing motor circuit.

The swing pressure sensor is critical for monitoring hydraulic pressure in the swing motor system, allowing the ECU to optimize swing performance, prevent overloading, and protect hydraulic components. On the R500LC-7A, this dual-swing motor system relies on accurate pressure feedback to balance loads during rotation operations. When this code appears, the machine's control system cannot reliably determine actual swing motor pressure, potentially compromising operator control and placing unnecessary stress on hydraulic components.

Common Symptoms

When Fault Code 718-11 is active, operators may experience:

• Illuminated warning light on the instrument cluster with reduced swing response or erratic swing behavior
• Swing operation entering derate mode, limiting rotational speed or torque output
• Intermittent or jerky swing movements, especially during high-load rotation operations
• ECU logging the fault even when swing appears to function normally (intermittent sensor voltage spikes)
• Abnormal hydraulic pressure readings displayed on the monitor (if equipped with pressure monitoring)

Potential Causes

The most common technical causes for Code 718-11 on used Hyundai excavators include:

• Damaged or corroded sensor connector at the swing motor pressure sensor (especially common in machines with 5,000+ operating hours)
• Chafed or pinched wiring harness between the sensor and ECU, particularly at pivot points near the swing bearing where harness flex occurs
• Failed pressure sensor with internal short circuit causing continuous high voltage output
• Water intrusion into the sensor connector or harness junction boxes (common in machines operated in wet conditions)
• ECU malfunction (less common) causing incorrect voltage interpretation or internal short
• Aftermarket or incorrect replacement sensor with incompatible voltage output specifications

How to Troubleshoot and Fix Code 718-11

Step 1: Visual Inspection and Connector Check Begin by locating the Swing Motor #2 pressure sensor on the secondary swing motor assembly. Disconnect the sensor connector and inspect both male and female pins for corrosion, bent pins, or moisture. On used excavators, pay special attention to the rubber sealing boot—deterioration here allows water ingress. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Circuit Voltage Testing Using a digital multimeter (DMM), backprobe the sensor signal wire at the connector (typically a 5-volt reference circuit). With the ignition key ON but engine OFF, measure voltage between the signal wire and chassis ground. Normal reading should be approximately 0.5-0.8 volts at zero pressure. If voltage exceeds 4.5 volts with the sensor disconnected, suspect a short to power in the harness or ECU issue.

Step 3: Harness Continuity and Resistance Testing Trace the sensor harness from the swing motor to the main harness junction near the cab, inspecting for rub points, pinch locations, or damaged insulation. Check resistance between signal wire and ground—should read open circuit (OL). Also verify 5-volt reference supply and sensor ground integrity using manufacturer wiring diagrams. For the R500LC-7A, the harness passes through a high-flex area near the center joint; inspect this routing carefully on used machines.

Step 4: Sensor Replacement and Verification If wiring checks pass but voltage remains high, replace the pressure sensor with a genuine Hyundai part (part number specific to R500LC-7A specifications). After installation, clear codes using Hi-MATE diagnostic software or compatible scan tool. Perform a swing pressure test cycle to verify proper sensor operation under load conditions.

Critical Note for Used Excavators: Before replacing sensors, always inspect harness routing for wear patterns specific to this model's 8,000-10,000 hour service history. Connector corrosion and harness abrasion at pivot points are far more common failure modes than actual sensor defects in field conditions.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hyundai service manual for your specific machine serial number, and consider professional diagnostic support for complex electrical issues. Improper repairs may void warranties or create safety hazards.