What is Komatsu PC160LC-7 Fault Code E315?

Fault Code E315 on the Komatsu PC160LC-7 indicates a malfunction in the swing motor solenoid valve circuit, specifically detecting an abnormal voltage or open circuit condition in the swing motor's proportional control system. This code is generated when the machine's Electronic Control Module (ECM) detects that the electrical signal to the swing motor's proportional solenoid valve falls outside the manufacturer's specified parameters, typically between 0.5-4.5 volts during normal operation.

This fault is critical for the PC160LC-7 because it directly impacts the excavator's ability to control swing speed and direction smoothly. The swing motor proportional solenoid regulates hydraulic flow to the swing motor, and any electrical disruption can result in erratic swing performance or complete loss of swing function. For used machines, this code often points to age-related wiring deterioration or connector corrosion rather than actual solenoid failure.

Common Symptoms

• Erratic or jerky swing motion during rotation, with inconsistent speed control even with smooth joystick input
• Complete loss of swing function while all other hydraulic functions (boom, arm, bucket) operate normally
• Warning light illumination on the instrument panel with possible audible alarm
• Swing motor operates only at full speed or not at all, with no proportional control available
• Intermittent swing operation that works occasionally then fails, especially during cold starts on older machines

Potential Causes

The most common causes for Code E315 on used PC160LC-7 excavators include:

• Damaged wiring harness near the swing motor mounting area where vibration and cable flex create wear points, particularly at the upper structure routing
• Corroded or moisture-contaminated connectors at the swing motor solenoid valve, especially in machines operating in wet or coastal environments
• Failed proportional solenoid valve within the swing motor assembly due to internal coil breakdown or mechanical sticking
• ECM internal circuit failure affecting the output driver for the swing solenoid control signal
• Broken or chafed wires at known rub points between the lower and upper structure where the harness passes through the center joint
• Poor ground connections at the swing motor mounting points causing erratic voltage readings

How to Troubleshoot and Fix Code E315

Step 1: Visual Inspection of Wiring and Connectors Start by disconnecting the battery and thoroughly inspecting the wiring harness from the ECM to the swing motor solenoid valve. On used excavators, pay special attention to the harness routing through the center joint where constant rotation creates friction points. Look for abraded insulation, broken wires, or signs of previous repairs. Check all connector pins for corrosion, bent terminals, or moisture intrusion—use electrical contact cleaner on suspect connectors.

Step 2: Electrical Testing with Multimeter Using a quality digital multimeter, measure the resistance of the solenoid coil with the connector disconnected. The proportional solenoid should read approximately 3-6 ohms (consult your PC160LC-7 service manual for exact specifications). Next, check for continuity along the entire wiring harness from the ECM connector to the solenoid connector. Any open circuit or resistance above 1 ohm indicates wiring damage.

Step 3: Voltage Supply and Signal Testing Reconnect the system and measure the voltage supply at the solenoid connector with the ignition on (engine off). You should see battery voltage (approximately 24V on this model). Using Komatsu diagnostic software (KOMTRAX or compatible tool), command the swing function and observe the control signal voltage at the solenoid. It should vary smoothly between 0.5-4.5 volts. If voltage is present but erratic, suspect ECM output issues. If no signal exists but wiring tests good, the ECM driver circuit has likely failed.

Step 4: Component Replacement and Verification If testing confirms a faulty solenoid valve, replace the proportional solenoid assembly on the swing motor. For used machines, consider replacing the entire connector pigtail if corrosion is evident, as this prevents recurring issues. After replacement, clear the fault code using diagnostic software, operate the swing function through full range, and verify smooth proportional control returns. Re-check for code reoccurrence after 30 minutes of operation.

Disclaimer: This guide provides general troubleshooting information for Code E315. Always consult the official Komatsu PC160LC-7 service manual and consider engaging a certified Komatsu technician for complex electrical diagnostics, especially when ECM replacement may be necessary. Improper electrical testing can cause additional damage to sensitive control modules.