What is Komatsu PC450-7 Fault Code E115?

Komatsu PC450-7 fault code E115 indicates a malfunction in the engine water temperature sensor circuit, specifically detecting an abnormal voltage signal being sent to the Engine Control Module (ECM). This code triggers when the ECM receives a voltage reading outside the expected range from the coolant temperature sensor, typically located near the thermostat housing on the SAA6D125E-3 engine.

The coolant temperature sensor plays a critical role in the PC450-7's performance by providing real-time data that the ECM uses to adjust fuel injection timing, manage engine warm-up cycles, and activate the cooling fan. When this sensor circuit fails, the engine cannot properly regulate its operating temperature, potentially leading to reduced efficiency, increased emissions, or inadequate protection against overheating in this 245-horsepower machine.

Common Symptoms

• Engine warning light illuminated on the instrument panel with code E115 displayed on the monitor screen
• Hard starting or rough idle, especially during cold starts when the ECM relies heavily on temperature data
• Cooling fan running continuously at high speed, even when the engine is cold
• Reduced engine power or activation of derate mode as the ECM enters a failsafe operational state
• Poor fuel economy due to the ECM defaulting to enriched fuel mapping without accurate temperature feedback

Potential Causes

The most common causes of E115 on used PC450-7 excavators include:

• Faulty coolant temperature sensor with internal resistance degradation (common after 8,000+ operating hours)
• Corroded or loose connector at the sensor plug, particularly on machines operated in wet or corrosive environments
• Damaged wiring harness between the sensor and ECM, with known rub points near the fuel filter bracket and engine mount
• Poor ground connection at the sensor circuit ground point on the cylinder head
• ECM internal fault (rare, but possible on high-hour machines with moisture infiltration)
• Coolant contamination causing sensor element coating and false readings

How to Troubleshoot and Fix Code E115

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor connector located on the engine's coolant outlet housing. On used excavators, check for corrosion, bent pins, or moisture intrusion in the connector. Disconnect the harness and examine both the sensor pins and connector terminals for green corrosion common in aged machines.

Step 2: Sensor Resistance Testing Using a digital multimeter, measure the sensor's resistance across its terminals with the engine cold. The SAA6D125E-3 sensor should read approximately 2,000-3,000 ohms at 68°F (20°C). Compare your reading to Komatsu's specification chart. A reading of infinite resistance or near-zero ohms indicates sensor failure requiring replacement (Komatsu part number 6732-81-3140).

Step 3: Wiring Harness Continuity Check Disconnect the sensor and test continuity and voltage in the harness. Check for 5-volt reference voltage from the ECM at the connector with the key on. Inspect the harness routing for wear points near the injection pump and valve cover, common failure locations on PC450-7 models with 10,000+ hours.

Step 4: Ground Circuit Verification Verify the sensor ground circuit has less than 0.5 ohms resistance to chassis ground. Poor grounding is especially common on used machines where corrosion accumulates at ground terminals on the cylinder head.

Step 5: Clear Code and Monitor After repairs, clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scanner. Run the engine through a complete heat cycle and monitor for code recurrence.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Komatsu service manual for your specific machine serial number and seek qualified diesel technician assistance for complex electrical diagnostics or ECM-related issues.