What is Komatsu PC160LC-7 Fault Code E318?

Fault Code E318 on the Komatsu PC160LC-7 indicates a Swing Motor Speed Sensor Circuit Malfunction. This diagnostic trouble code is triggered when the Electronic Control Module (ECM) detects an abnormal signal or no signal from the swing motor speed sensor, which monitors the rotational speed of the upper structure during slewing operations.

The swing motor speed sensor is critical for the PC160LC-7's operational efficiency and safety. This sensor provides real-time data to the ECM, enabling the controller to optimize hydraulic flow, manage swing brake engagement timing, and prevent mechanical shock during sudden directional changes. When this sensor circuit fails, the machine's swing function may enter a protective derate mode, limiting productivity and potentially compromising jobsite safety during lifting or material handling operations.

Common Symptoms

When Code E318 is active on your Komatsu PC160LC-7, operators typically experience:

• Swing function derate or complete loss of upper structure rotation capability
• Illuminated warning lamp on the instrument cluster, often accompanied by an audible alarm
• Erratic swing motor performance, including jerky movements or inconsistent acceleration during slewing
• Stored fault code in the ECM that persists even after ignition cycles
• Reduced swing speed or failure to engage swing brake properly, creating safety concerns

Potential Causes

Based on field diagnostics for used PC160LC-7 excavators, the most common causes include:

• Damaged or severed sensor wiring in the swing motor harness, particularly at flex points near the center joint where cables experience constant rotation stress
• Corroded or loose electrical connectors at the sensor plug or ECM terminals, common in machines with high hour accumulation or exposure to moisture
• Failed swing motor speed sensor due to internal component degradation, bearing wear contamination, or impact damage
• Short circuit or open circuit in the sensor supply voltage (typically 8-12V) or ground circuit
• ECM internal fault (less common) affecting the sensor input circuit processing

How to Troubleshoot and Fix Code E318

Step 1: Visual Inspection Begin by inspecting the swing motor speed sensor harness from the sensor location to the ECM connection. On used excavators, focus on known wear points at the center joint rotary coupling and anywhere the harness contacts metal surfaces. Check for abraded insulation, pinched wires, or visible corrosion on connector terminals.

Step 2: Electrical Testing Using a digital multimeter, verify sensor power supply voltage at the sensor connector (should read 8-12V with ignition on). Test sensor resistance according to Komatsu specifications (typically 800-1,200 ohms). Check for continuity between sensor ground and chassis ground, and verify no shorts to voltage.

Step 3: Signal Verification Connect Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor live sensor data during swing operation. The signal should show predictable voltage changes corresponding to rotation speed. If no signal appears despite proper voltage/ground, replace the speed sensor.

Step 4: Connector and Harness Repair For used machines, clean all connector pins with electrical contact cleaner and apply dielectric grease. Repair any damaged wiring using proper gauge wire and heat-shrink connections. Ensure proper routing to prevent future abrasion.

Disclaimer: This guide provides general diagnostic procedures. Always consult the official Komatsu PC160LC-7 service manual and qualified heavy equipment technicians for complex electrical diagnostics and repairs.