Kobelco SK135SRLC-2 Fault Code R144: Technical Guide

What is Kobelco SK135SRLC-2 Fault Code R144?

Fault Code R144 indicates a malfunction in the engine oil pressure sensor circuit or abnormally low oil pressure detected by the Engine Control Module (ECM). This code triggers when the ECM receives voltage readings outside the expected range from the oil pressure sensor, or when actual oil pressure falls below the manufacturer's specified threshold during engine operation.

In the Kobelco SK135SRLC-2, the oil pressure sensor monitors critical engine lubrication to protect the Hino J05E diesel engine. When this code activates, the ECM may initiate protective measures including power derate or automatic shutdown to prevent catastrophic engine damage. This protection system is especially important in used excavators where oil system wear naturally increases over time.

Common Symptoms

When Code R144 is active, operators typically experience:

• Engine warning light illuminated on the dashboard (often red oil can symbol)
• Audible alarm or buzzer indicating critical engine fault
• Automatic engine power reduction (derate mode) limiting machine performance
• Engine shutdown after a brief warning period if pressure remains critically low
• Rough idle or hesitation during hydraulic work cycles due to ECM intervention

Potential Causes

The most frequent technical causes for Code R144 on used SK135SRLC-2 excavators include:

• Failed oil pressure sensor – common failure point after 5,000+ operating hours
• Low engine oil level due to leaks or consumption in high-hour machines
• Damaged wiring harness between sensor and ECM, particularly where harness runs near engine mount brackets (known rub point)
• Corroded or loose electrical connectors at the sensor or ECM terminals
• Worn oil pump unable to maintain adequate pressure at operating temperature
• Clogged oil filter restricting flow and reducing system pressure
• Excessive bearing clearances in high-hour engines causing pressure loss

How to Troubleshoot and Fix Code R144

Step 1: Verify Oil Level and Quality Check engine oil level with machine on level ground. Inspect oil condition for contamination or metallic particles indicating internal wear. Top off or change oil if necessary using Hino-approved 10W-30 or 15W-40 diesel engine oil.

Step 2: Inspect Oil Pressure Sensor and Wiring Locate the oil pressure sensor on the engine block's left side near the oil filter housing. Disconnect the electrical connector and inspect for:

• Corrosion on pins (clean with electrical contact cleaner)
• Damaged weather seal (replace if cracked)
• Wire insulation damage along harness routing points

Step 3: Test Sensor Electrical Values Using a digital multimeter, measure sensor resistance (typically 100-300 ohms at room temperature). With ignition ON/engine OFF, check supply voltage at connector (should read approximately 5 volts from ECM). Values outside this range indicate sensor replacement needed (Kobelco part number YN52S00039P1).

Step 4: Verify Actual Oil Pressure Install a mechanical oil pressure gauge in the sensor port. Start engine and verify pressure meets specifications (typically 280-430 kPa / 40-62 psi at operating temperature and 2000 RPM). If mechanical gauge shows adequate pressure but code persists, replace the sensor. If pressure is genuinely low, investigate oil pump wear or bearing clearances.

Step 5: Inspect ECM Connections Check ECM connector terminals for corrosion or backed-out pins. On used excavators, vibration often loosens these connections over time.

---

Disclaimer: This guide provides general troubleshooting information. For used excavators with complex issues or if you lack proper diagnostic tools, consult a certified Kobelco technician or heavy equipment mechanic. Improper diagnosis may result in severe engine damage.