Komatsu PC400-7 Fault Code E117: Complete Diagnostic Guide

What is Komatsu PC400-7 Fault Code E117?

Fault Code E117 on the Komatsu PC400-7 indicates a hydraulic oil temperature sensor circuit malfunction or abnormal signal from the main hydraulic system temperature monitoring circuit. This code is triggered when the Engine Control Module (ECM) detects voltage readings outside the expected range (typically 0.5-4.5V) from the hydraulic oil temperature sensor, signaling either an open circuit, short circuit, or sensor degradation.

This fault is critical for the PC400-7 because the hydraulic oil temperature directly affects system efficiency, component longevity, and operational safety. The monitor system uses this data to prevent catastrophic overheating damage to pumps, motors, and seals. When this sensor fails, the machine may enter a protective derate mode or display inaccurate temperature readings, risking expensive hydraulic component failure.

Common Symptoms

When Code E117 is active, operators typically experience:

• Warning lamp illumination on the instrument cluster (hydraulic temperature warning light)
• Inaccurate or frozen temperature gauge readings on the monitor display
• Reduced hydraulic performance if the ECM activates protective power limitations
• Intermittent code appearance during warm-up or after extended operation (indicating connection issues)
• Alarm buzzer activation in some configurations when combined with actual high oil temperatures

Potential Causes

The most common technical reasons for E117 on used PC400-7 excavators include:

• Sensor degradation or internal failure of the hydraulic oil temperature sensor (common after 8,000+ hours)
• Corroded or loose connector pins at the sensor harness connection point near the hydraulic tank
• Damaged wiring harness due to rubbing against the tank mounting bracket or hydraulic lines (known wear point on PC400 series)
• ECM internal circuit malfunction (rare, but possible in high-hour machines)
• Contamination or moisture intrusion in the connector causing intermittent short circuits
• Voltage supply issues from the main power harness affecting multiple sensor circuits

How to Troubleshoot and Fix Code E117

Step 1: Visual Inspection and Connector Check

Locate the hydraulic oil temperature sensor mounted on the hydraulic tank (typically on the right side near the return filter). Disconnect the sensor connector and inspect for corrosion, bent pins, or oil contamination. On used excavators, this connector frequently shows green corrosion on the terminals. Clean with electrical contact cleaner and apply dielectric grease.

Step 2: Sensor Resistance Testing

Using a digital multimeter, measure the sensor resistance. At room temperature (20°C/68°F), resistance should read approximately 2,000-3,000 ohms (verify exact specification in service manual). Warm the sensor with a heat gun while monitoring resistance—it should decrease smoothly as temperature increases. Erratic or infinite readings indicate sensor failure. For used machines, thermal cycling often causes internal sensor element cracking.

Step 3: Circuit Voltage and Harness Testing

With the connector attached and ignition ON (engine OFF), backprobe the signal wire at the ECM connector. You should read approximately 5V reference voltage. Check for voltage drops along the harness, especially where the wire passes through bulkhead grommets and near metal edges—common harness rub points on the PC400-7. Repair any damaged insulation with heat-shrink tubing and re-route away from sharp edges.

Step 4: ECM Signal Verification

Connect Komatsu diagnostic software (KOMTRAX or PC Service Tool) to monitor live sensor data. Compare displayed temperature with actual hydraulic oil temperature using an infrared thermometer. If the sensor tests good but ECM shows erroneous readings, suspect ECM internal circuit damage or poor ECM ground connections (check main chassis ground straps for corrosion).

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Disclaimer: This guide provides general diagnostic procedures for experienced technicians. Always consult the official Komatsu PC400-7 service manual for complete specifications and safety procedures. If unfamiliar with electrical diagnostics or working around hydraulic systems, consult a certified Komatsu technician to prevent injury or further equipment damage.