Komatsu PC220-10 Fault Code CA698: Complete Diagnostic Guide

What is Komatsu PC220-10 Fault Code CA698?

Fault Code CA698 indicates a malfunction in the engine coolant temperature sensor circuit, specifically detecting an abnormal voltage signal or open circuit condition in the coolant temperature monitoring system. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) receives voltage readings outside the acceptable range from the coolant temperature sensor, typically below 0.2V or above 4.8V on the 5V reference circuit.

This code is critical for the PC220-10 because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine protection systems, and manage hydraulic oil temperature. When CA698 activates, the ECM enters a default mode that can significantly impact machine performance and potentially cause engine damage if the actual coolant temperature exceeds safe operating limits.

Common Symptoms

When CA698 is active on your Komatsu PC220-10, you may experience:

• Engine warning light illuminated on the monitor panel with possible temperature gauge reading abnormally high or low (often showing -40°C or maximum)
• Engine power derate or reduced hydraulic response as the ECM enters protective mode
• Difficulty starting the engine, especially in cold conditions, due to improper fuel management
• Cooling fan running continuously at maximum speed regardless of actual engine temperature
• Black smoke from exhaust caused by incorrect fuel-to-air mixture calculations

Potential Causes

The most common technical reasons for CA698 on used PC220-10 excavators include:

• Coolant temperature sensor failure due to internal element degradation (common after 5,000-8,000 operating hours)
• Corroded or damaged wiring harness connectors at the sensor plug, especially where the harness routes near the turbocharger heat shield
• Chafed wiring along the engine harness run between the sensor and ECM, particularly at chassis rub points near the hydraulic pump mounting bracket
• Failed ECM coolant temperature input circuit due to moisture intrusion or voltage spike damage
• Poor ground connection at the sensor mounting point caused by corrosion or improper sensor installation

How to Troubleshoot and Fix Code CA698

Step 1: Visual Inspection and Connector Check Begin by locating the coolant temperature sensor on the engine block near the thermostat housing. Disconnect the sensor 2-pin connector and inspect for corrosion, bent pins, or moisture. On used excavators, check for green corrosion buildup—clean with electrical contact cleaner and dielectric grease. Inspect the wiring harness from sensor to ECM for obvious chafing, especially where it contacts metal edges.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure resistance across the sensor terminals with the engine cold. A functional sensor should read approximately 2,000-3,000 ohms at 20°C (68°F). Compare your reading to the Komatsu resistance-temperature chart in the service manual. If resistance is infinite (open circuit) or near zero (short circuit), replace the sensor with a genuine Komatsu part (PN: 6732-81-3140 or equivalent).

Step 3: Circuit Voltage and Wiring Verification With the sensor disconnected and ignition ON (engine OFF), measure voltage at the harness connector. You should see approximately 5V reference voltage on one pin and continuity to ground on the other. If voltage is absent, check for harness continuity between the sensor connector and ECM pins using the wiring diagram. For used machines, pay special attention to harness sections that experience heat cycling—remove protective loom and inspect for brittle, cracked insulation that could cause intermittent shorts.

Step 4: ECM Input Verification If the sensor and wiring test correctly, the issue may lie within the ECM's temperature input circuit. Connect Komatsu KOMTRAX diagnostic software or an aftermarket scan tool to monitor live coolant temperature data. Simulate temperature changes using a heat gun on the sensor while monitoring—erratic readings indicate ECM internal failure requiring module replacement or reprogramming.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Komatsu PC220-10 service manual and safety procedures. If you're uncomfortable performing electrical diagnostics, contact a certified Komatsu dealer or qualified heavy equipment technician to prevent further damage to your machine.