Komatsu PC850-8R Fault Code E-22: Complete Diagnostic Guide

What is Komatsu PC850-8R Fault Code E-22?

Fault Code E-22 on the Komatsu PC850-8R indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal coolant temperature reading. This code is triggered when the Electronic Control Module (ECM) detects voltage signals outside the normal operating range from the coolant temperature sensor, typically between 0.5-4.5 volts.

The coolant temperature sensor is critical for the PC850-8R's performance management system. It directly influences fuel injection timing, engine protection protocols, and hydraulic oil temperature regulation. When this sensor fails or provides inaccurate data, the ECM cannot properly manage engine operations, potentially leading to reduced efficiency, overheating, or unnecessary engine derating.

Common Symptoms

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

• Warning light illumination on the instrument cluster, often accompanied by an audible alarm
• Engine derate mode activation, limiting maximum RPM to protect components
• Erratic temperature gauge readings or gauge stuck at minimum/maximum positions
• Difficulty starting in cold conditions due to improper fuel enrichment
• Increased fuel consumption as the ECM defaults to safe-mode fuel mapping

Potential Causes

The most common technical causes for E-22 on used PC850-8R excavators include:

• Coolant temperature sensor failure due to age-related degradation or thermal cycling damage
• Wiring harness damage at known rub points near the engine block mounting brackets
• Corroded or loose connector pins at the sensor plug, especially on machines operating in harsh environments
• ECM internal circuit failure (less common but possible on high-hour machines)
• Damaged sensor ground wire or poor chassis ground connection
• Coolant contamination causing sensor element coating or failure

How to Troubleshoot and Fix Code E-22

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor located on the engine block's coolant passage. Check the wiring harness for abrasion, particularly where it routes near moving components or sharp edges. On used excavators, examine connector pins for corrosion, bent terminals, or moisture intrusion—common issues after years of operation.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across its terminals. At 68°F (20°C), resistance should typically read 2,000-3,000 ohms (consult your service manual for exact specifications). Test harness continuity from the sensor connector back to the ECM pins. Check for shorts to ground or power using the multimeter's continuity function.

Step 3: Live Data Analysis Connect Komatsu diagnostic software (KOMTRAX Plus or equivalent) to monitor real-time sensor voltage. Compare readings against actual coolant temperature using an infrared thermometer. Voltage should decrease smoothly as temperature rises. Erratic readings indicate sensor failure; no change suggests open circuit or ECM issues.

Step 4: Component Replacement If testing confirms sensor failure, replace with genuine Komatsu parts to ensure proper calibration. Before installation on used equipment, clean the sensor mounting bore and apply appropriate thread sealant. After replacement, clear codes and perform a cold-start test cycle to verify proper operation.

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Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC850-8R service manual and consider professional technician assistance for complex electrical diagnostics or if you're unfamiliar with high-voltage systems.