What is Komatsu PC1250-11R Fault Code CA273?

Fault Code CA273 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low engine oil pressure detected by the Engine Control Module (ECM). This code specifically relates to the oil pressure monitoring system that protects the Komatsu SAA6D170E-5 engine from catastrophic damage due to inadequate lubrication.

The oil pressure sensor sends real-time voltage signals to the ECM, which continuously monitors whether oil pressure remains within the manufacturer's specified range during operation. On the PC1250-11R, proper oil pressure is critical for lubricating the turbocharger, main bearings, and hydraulic pump drive components. When CA273 triggers, the ECM may initiate engine derate mode or shutdown protocols to prevent severe internal engine damage, making immediate diagnosis essential for operational safety and equipment longevity.

Common Symptoms

• Warning lamp illumination on the monitor panel, often accompanied by an audible alarm
• Engine power reduction (derate mode) limiting machine performance to protect internal components
• Erratic oil pressure gauge readings or gauge showing zero pressure despite engine running normally
• Engine shutdown during operation, particularly under load or at operating temperature
• Diagnostic trouble code stored in ECM memory, retrievable via Komatsu diagnostic software

Potential Causes

The most common technical failures triggering CA273 on used PC1250-11R excavators include:

• Failed oil pressure sensor due to internal diaphragm fatigue or contamination from metal particles in aged oil
• Damaged wiring harness between the sensor and ECM, particularly at known rub points near the engine mount brackets and along the frame rail
• Corroded or loose electrical connectors at the sensor terminal, especially on machines operating in high-moisture environments
• Actual low engine oil pressure caused by worn oil pump, clogged oil filter, or excessive bearing clearances in high-hour machines
• ECM calibration issues or software glitches requiring reprogramming with Komatsu KOMTRAX diagnostic tools

How to Troubleshoot and Fix Code CA273

Step 1: Visual Inspection Begin by checking actual engine oil level and condition. Inspect the oil pressure sensor (located on the engine block near the oil filter housing) for physical damage, oil leaks, or corroded connections. On used excavators, examine the wiring harness for chafing, particularly where it contacts frame components or passes through bulkheads.

Step 2: Electrical Testing Using a digital multimeter, check sensor signal voltage with key-on/engine-off (should read approximately 0.5V) and compare to running values (typically 2.5-4.5V depending on pressure). Measure harness resistance between sensor connector and ECM pins—readings above 5 ohms indicate wiring degradation. Check for short circuits to ground.

Step 3: Mechanical Verification Install a calibrated mechanical oil pressure gauge at the test port to verify actual pressure against sensor readings. Komatsu specifies minimum 2.8 kg/cm² at idle and 5.0-6.0 kg/cm² at rated RPM for this engine. If mechanical pressure is correct but sensor reads incorrectly, replace the sensor. If actual pressure is low, investigate oil pump wear or internal engine problems.

Step 4: Component Replacement and Verification Replace faulty sensors with genuine Komatsu parts (P/N 6754-21-6110 or equivalent). Clear codes using Komatsu diagnostic software, test operation under load, and monitor for code recurrence during a complete work cycle.

---

Disclaimer: This guide provides general diagnostic information. Always consult the official Komatsu PC1250-11R service manual and consider professional diagnostic assistance for complex issues, especially on high-value used equipment.