What is Komatsu PC110-8M0 Fault Code CA272?

Fault Code CA272 indicates a malfunction in the engine coolant temperature sensor circuit or an abnormal engine coolant temperature reading detected by the Engine Control Module (ECM). This diagnostic trouble code (DTC) specifically signals that the ECM has identified either an implausible voltage signal from the coolant temperature sensor or a detected temperature value outside the acceptable operating range for the Komatsu SAA4D107E-2 engine in the PC110-8M0 excavator.

This code is critical for the PC110-8M0's performance because the ECM relies on accurate coolant temperature data to optimize fuel injection timing, control engine warm-up cycles, and prevent overheating damage. When CA272 is active, the engine management system may default to a predetermined temperature value, potentially causing inefficient combustion, increased fuel consumption, or activation of engine protection modes that limit machine productivity.

Common Symptoms

When fault code CA272 is active on your Komatsu PC110-8M0, you may experience:

• Engine warning lamp illuminated on the instrument cluster, sometimes accompanied by a coolant temperature warning icon
• Engine operating in derate mode with reduced power output, especially noticeable during digging or lifting operations
• Difficulty starting the engine when cold, or prolonged warm-up periods with rough idling
• Cooling fan running continuously at high speed, even when the engine appears to be at normal operating temperature
• Inconsistent or erratic coolant temperature gauge readings that don't correlate with actual engine temperature

Potential Causes

Several technical issues can trigger CA272 on used PC110-8M0 excavators:

• Coolant temperature sensor failure due to internal thermistor degradation (common after 5,000+ operating hours)
• Corroded or loose electrical connections at the sensor connector or ECM harness pins
• Wiring harness damage caused by chafing against the engine block near the thermostat housing—a known wear point on this model
• Faulty ECM with internal circuit board issues affecting the temperature signal processing
• Actual engine overheating condition caused by cooling system failures (low coolant, failed thermostat, or radiator blockage)
• Contaminated engine coolant causing sensor element fouling or crystallization on the sensor tip

How to Troubleshoot and Fix Code CA272

Step 1: Visual Inspection Begin by inspecting the coolant temperature sensor location on the cylinder head near the thermostat housing. Check for coolant leaks, corrosion on the connector, or obvious wiring damage. On used excavators, carefully examine the harness routing for signs of rubbing against the engine—this is a frequent failure point on PC110-8M0 machines.

Step 2: Electrical Testing Disconnect the coolant temperature sensor connector and measure resistance across the sensor terminals using a digital multimeter. At approximately 20°C (68°F), you should read between 2,000-3,000 ohms; at 80°C (176°F), resistance should drop to approximately 300-400 ohms. Compare your readings to Komatsu specifications. Also check for continuity in the wiring harness between the sensor connector and ECM pins.

Step 3: Signal Voltage Verification With the sensor connected and ignition on (engine off), use Komatsu diagnostic software (KOMTRAX or compatible scan tool) to monitor live coolant temperature voltage. The signal should typically range from 0.5V to 4.5V depending on temperature. Values stuck at 0V or 5V indicate open circuit or short circuit conditions respectively.

Step 4: Component Replacement and Verification If testing confirms sensor failure, replace with a genuine Komatsu coolant temperature sensor (part number 6732-81-3210 or equivalent). For used machines, always apply dielectric grease to connector pins to prevent future corrosion. After replacement, clear the fault code, run the engine through a complete warm-up cycle, and verify CA272 does not return.

---

Disclaimer: This guide provides general troubleshooting information for Komatsu PC110-8M0 fault code CA272. Always consult the official Komatsu service manual for your specific machine serial number and seek professional diagnostic assistance if you're uncertain about any procedure. Improper repairs may cause additional damage or safety hazards.