What is Komatsu PC400-7 Fault Code E113?

Fault Code E113 on the Komatsu PC400-7 excavator indicates a Hydraulic Oil Temperature Sensor Circuit Malfunction. This diagnostic trouble code is triggered when the Engine Control Module (ECM) detects an abnormal voltage signal from the hydraulic oil temperature sensor, which monitors the temperature of the hydraulic fluid in the main hydraulic system.

The hydraulic oil temperature sensor plays a critical role in protecting the PC400-7's hydraulic system from overheating. This sensor sends continuous voltage signals to the ECM, which uses this data to adjust pump output, activate cooling fans, and prevent component damage. When the sensor circuit fails or provides readings outside the normal range (typically 0.5-4.5 volts), the ECM cannot accurately monitor hydraulic temperatures, potentially leading to reduced machine performance or automatic derating to prevent catastrophic hydraulic system failure.

Common Symptoms

• Hydraulic oil temperature warning light illuminated on the instrument panel
• Reduced hydraulic performance or sluggish operation as the ECM enters protective derate mode
• Cooling fan running continuously at high speed, even when hydraulic temperatures are normal
• Error messages displayed on the multi-information display indicating hydraulic system faults
• Machine may enter limited operation mode, restricting swing speed or attachment functions

Potential Causes

The E113 fault code on used PC400-7 excavators typically stems from several common failure points. Sensor connector corrosion is extremely prevalent on machines operating in wet or coastal environments, as moisture infiltrates the connector terminals. Wiring harness damage near the hydraulic tank is another frequent culprit—the harness routing on this model is susceptible to rubbing against the tank mounting bracket, causing chafed wires and intermittent short circuits.

Failed hydraulic oil temperature sensor itself is common after 5,000+ operating hours due to thermal cycling and exposure to hot hydraulic fluid. ECM internal faults are less common but possible on high-hour machines. Additionally, poor grounding connections at the sensor mounting point can create erratic voltage readings that trigger this code.

How to Troubleshoot and Fix Code E113

Step 1: Visual Inspection Begin by locating the hydraulic oil temperature sensor mounted on the main hydraulic tank (typically on the left side near the return filter). Inspect the sensor connector for corrosion, oil contamination, or pushed-back pins. Check the wiring harness from the sensor to the ECM for visible damage, particularly where it routes near the tank bracket—this is a known rub point on used PC400-7 machines.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals. At room temperature (68°F/20°C), resistance should read approximately 2,000-3,000 ohms; consult your service manual for exact specifications. Check for voltage supply at the harness connector—you should see approximately 5 volts reference voltage from the ECM with ignition on.

Step 3: Circuit Continuity and Ground Testing Test continuity between the sensor connector and ECM pins to identify broken wires. Inspect the sensor ground connection at the mounting threads; clean any corrosion and apply anti-seize compound. If voltage and continuity tests pass, the sensor itself is likely faulty and requires replacement with a genuine Komatsu sensor (Part# 7861-93-1650 or equivalent).

Step 4: Clear Code and Monitor After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool. Operate the machine through a full work cycle while monitoring live sensor data to confirm the repair resolved the issue.

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC400-7 service manual and consider professional assistance from certified technicians for complex electrical diagnostics or if you're uncomfortable performing these procedures.