Komatsu PC750-7 Fault Code E-22: Complete Diagnostic Guide

What is Komatsu PC750-7 Fault Code E-22?

Fault Code E-22 on the Komatsu PC750-7 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 irregular voltage signals outside the manufacturer's specified parameters, typically between 0.5-4.5 volts.

This fault is critical for the PC750-7's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine speed, and prevent overheating damage to the Komatsu SAA6D140E-5 engine. When E-22 triggers, the system may enter a protective derate mode to prevent catastrophic engine failure.

Common Symptoms

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

• Engine warning light illuminated on the instrument cluster with possible audible alarm
• Reduced engine power or automatic derate limiting machine performance to 70-80% capacity
• Erratic temperature gauge readings showing unusually high or low coolant temperatures
• Hard starting conditions, especially in cold weather, due to incorrect fuel mapping
• Increased fuel consumption as the ECM defaults to a fail-safe enrichment strategy

Potential Causes

The most common technical causes for E-22 on used PC750-7 excavators include:

• Faulty coolant temperature sensor (part #6732-81-3210) due to internal resistance drift after 8,000+ operating hours
• Corroded or loose connector pins at the sensor harness connection point near the thermostat housing
• Damaged wiring harness with insulation wear at known rub points along the right-side engine valley
• Contaminated coolant causing sensor element coating and inaccurate readings
• ECM internal fault (rare) affecting the temperature input circuit
• Poor ground connection at the engine block grounding strap

How to Troubleshoot and Fix Code E-22

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine's thermostat housing. Check the connector for corrosion, moisture intrusion, or bent pins—common issues in used excavators exposed to harsh environments. Examine the wiring harness for chafing against engine components or heat damage.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 20°C (68°F), resistance should read approximately 2,000-3,000 ohms. Compare readings against Komatsu's specification chart. Next, check voltage supply at the harness connector with ignition on—should read approximately 5 volts from the ECM.

Step 3: Sensor Replacement and Verification If readings are out of specification, replace the coolant temperature sensor using genuine Komatsu parts. Before installation, apply dielectric grease to connector pins to prevent future corrosion. Clear the fault code using Komatsu diagnostic software (KOMTRAX) or a compatible scan tool, then monitor for code recurrence during a complete heat cycle.

Critical for Used Equipment: Always inspect harness routing and secure any loose wiring that may have shifted over years of vibration. Check coolant condition and flush if contaminated.

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Disclaimer: This guide provides general diagnostic information. Always consult Komatsu service manuals and qualified diesel technicians for complex repairs. Improper diagnosis may cause additional damage.