Komatsu PC360-8M0 Fault Code E-20: Complete Diagnostic Guide

What is Komatsu PC360-8M0 Fault Code E-20?

Fault Code E-20 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading detected by the Engine Control Module (ECM). This code specifically relates to the coolant temperature sensor sending incorrect voltage signals or detecting temperatures outside the normal operating range (typically -40°C to 150°C).

For the PC360-8M0's SAA6D114E engine, accurate coolant temperature monitoring is critical for proper fuel injection timing, engine protection systems, and hydraulic oil temperature management. When this code activates, the ECM may default to a predetermined temperature value, potentially affecting engine performance and fuel efficiency.

Common Symptoms

When Code E-20 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel with E-20 displayed
• Hard starting or extended cranking time, especially in cold conditions
• Engine derate mode activated, limiting maximum RPM to protect components
• Cooling fan running continuously at high speed regardless of actual temperature
• Black smoke from exhaust due to improper fuel-air mixture from incorrect temperature compensation

Potential Causes

The most common technical causes for E-20 on used PC360-8M0 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 8,000+ operating hours)
• Wiring harness damage at the sensor connector or along the routing path near the turbocharger where heat and vibration cause insulation breakdown
• Corroded or loose connector pins at the sensor or ECM connection points, particularly on machines operated in coastal or high-humidity environments
• ECM internal circuit failure affecting the temperature input channel (rare but documented in 2012-2014 production units)
• Coolant contamination causing sensor element coating and false readings
• Ground circuit issues specific to the engine harness ground point near the fuel filter base

How to Troubleshoot and Fix Code E-20

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's water jacket (driver's side, near cylinder #1). Check for coolant leaks, corrosion on the connector, or physical damage. On used excavators, examine the wiring harness for rub points against the engine block, especially where it passes near the alternator bracket—a known wear location on this model.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms. Compare readings with Komatsu's temperature-resistance chart. Next, check the signal wire voltage at the ECM connector (Pin 47 on the C1 connector): it should show approximately 5 volts with the sensor disconnected.

Step 3: Circuit Verification Test for continuity between the sensor connector and ECM pins, and check for short circuits to ground. Resistance should be less than 5 ohms for continuity and infinite for ground shorts. Pay special attention to the harness section near the hydraulic pump mounting bracket where vibration-induced wire fatigue is common in machines with 5,000+ hours.

Step 4: Component Replacement and Verification If sensor resistance is out of specification, replace with a genuine Komatsu part (6732-81-3110) or equivalent. After replacement, clear codes using Komatsu diagnostic software (KOMTRAX Plus) or a compatible scan tool, and monitor coolant temperature readings during a complete warm-up cycle. Verify the reading climbs smoothly from ambient to approximately 82-88°C operating temperature.

For used excavators: Before replacing the sensor, thoroughly clean all connector contacts with electrical contact cleaner and apply dielectric grease. Inspect the coolant condition—contaminated coolant often causes premature sensor failure and should be flushed if discolored or containing debris.

---

Disclaimer: This guide provides general diagnostic procedures. Complex electrical issues or ECM programming should be performed by certified Komatsu technicians with proper diagnostic equipment. Always consult the official service manual for your specific machine serial number and follow safety protocols when working on electrical systems.