Komatsu PC800SE-8R Fault Code E-22: Complete Diagnostic Guide

What is Komatsu PC800SE-8R Fault Code E-22?

Fault Code E-22 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 temperature monitoring system that protects the Komatsu SAA6D140E-7 engine from overheating damage.

The coolant temperature sensor provides critical data to the ECM, which uses this information to adjust fuel injection timing, control engine speed, and activate warning systems. On the PC800SE-8R, this sensor failure is particularly serious because the machine's advanced hydraulic systems and high-output engine generate substantial heat during heavy excavation work. Ignoring this code can lead to catastrophic engine damage, including warped cylinder heads, blown head gaskets, or complete engine seizure.

Common Symptoms

When Code E-22 is active, operators typically experience:

• Engine warning light illuminated on the monitor panel, often accompanied by an audible alarm
• Engine derate mode activated, limiting machine power output to 50-70% capacity to prevent overheating
• Erratic temperature gauge readings that fluctuate abnormally or show maximum temperature immediately at startup
• Reduced hydraulic performance due to ECM limiting engine RPM as a protective measure
• Difficulty starting in cold conditions if the ECM receives incorrect low-temperature signals

Potential Causes

The most common technical causes for E-22 on used PC800SE-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling damage (typical lifespan: 5,000-8,000 hours)
• Corroded or loose electrical connectors at the sensor harness connection point near the thermostat housing
• Damaged wiring harness caused by rubbing against the engine block or exhaust components—a known wear point on this model
• ECM internal fault affecting the temperature input circuit (less common but possible in high-hour machines)
• Actual coolant system problems including low coolant level, air pockets, or failed thermostat causing genuine overheating

How to Troubleshoot and Fix Code E-22

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the left side of the engine block near the thermostat housing. Check for physical damage, coolant leaks, or corrosion on the two-pin connector. On used excavators, examine the wiring harness for abrasion points where it contacts metal surfaces—this is a common failure point after 6,000+ operating hours.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure its resistance. At 68°F (20°C), resistance should read approximately 2,000-3,000 ohms; at 176°F (80°C), it should drop to 200-400 ohms. Also check for continuity in the harness wiring from sensor to ECM connector (pins typically labeled THW and E2). Resistance should be less than 1 ohm with no shorts to ground.

Step 3: Advanced Diagnostics Connect Komatsu KOMTRAX diagnostic software or a compatible scan tool to read live sensor data. Compare actual coolant temperature (use an infrared thermometer on the engine) with ECM-reported values. A variance greater than 15°F indicates sensor failure. Clear the code and monitor—if E-22 returns immediately without temperature change, suspect ECM circuit board issues.

Step 4: Repair and Prevention Replace the faulty sensor with a genuine Komatsu part (P/N 6732-81-3140 or equivalent) and apply dielectric grease to connector pins. For used machines, consider installing protective wire loom over exposed harness sections and securing with new zip ties away from heat sources.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu service manual for your specific serial number and consider professional assistance for complex electrical diagnostics or if you lack proper diagnostic equipment.