What is Hitachi ZX350LCK-5G Fault Code 16605-2?

Fault Code 16605-2 indicates a malfunction in the Engine Oil Pressure Sensor Circuit - specifically a low voltage condition or open circuit detected by the Engine Control Module (ECM). This code triggers when the sensor signal voltage falls below the manufacturer's specified threshold, typically under 0.5 volts, suggesting either a sensor failure, wiring issue, or poor ground connection.

The oil pressure sensor is critical for the ZX350LCK-5G's Isuzu engine management system, providing real-time data that protects against catastrophic engine damage. When this circuit fails, the ECM cannot accurately monitor lubrication system performance, potentially allowing the engine to operate under dangerous low-pressure conditions without proper warnings or protective shutdown protocols.

Common Symptoms

• Engine oil pressure warning lamp illuminated continuously on the instrument cluster
• Check Engine Light (CEL) or malfunction indicator lamp activation
• Possible engine derate mode or power limitation to protect the engine from potential damage
• Inaccurate or zero oil pressure readings on the digital display, even when engine is running normally
• ECM may store the code in memory even if the symptom is intermittent, requiring diagnostic tool retrieval

Potential Causes

The most common causes for Code 16605-2 on used ZX350LCK-5G excavators include:

• Faulty oil pressure sensor due to internal electrical failure or contamination from oil degradation (common after 5,000+ hours)
• Damaged wiring harness near the engine block where heat and vibration cause insulation breakdown
• Corroded or loose connector at the sensor or ECM interface points, especially on machines exposed to wet environments
• Broken or frayed wires at known rub points between the engine and chassis frame
• Poor ground connection at the sensor mounting point due to rust or thread damage
• ECM internal fault (rare, but possible on high-hour used machines with electrical system history)

How to Troubleshoot and Fix Code 16605-2

Step 1: Visual Inspection Begin with a thorough examination of the oil pressure sensor located on the engine block's left side. Check the connector for corrosion, moisture, or bent pins. Inspect the wiring harness from sensor to ECM for visible damage, especially where it contacts hot engine components or sharp edges.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor and measure resistance across the sensor terminals (typical specification: 50-200 ohms at 20°C). Next, check for voltage supply at the harness connector with ignition on—you should see approximately 5 volts reference voltage from the ECM. Test ground continuity between the sensor ground circuit and chassis ground (should read less than 1 ohm).

Step 3: Signal Wire Testing With the sensor connected and engine running, backprobe the signal wire and verify voltage changes with engine RPM (typically 0.5-4.5 volts). On used excavators, pay special attention to intermittent connections by wiggling harnesses while monitoring voltage—fluctuations indicate damaged wiring requiring repair or replacement.

Step 4: Component Replacement If testing confirms sensor failure, replace with genuine Hitachi or OEM-equivalent parts. For wiring issues, repair damaged sections using proper marine-grade heat shrink and ensure routing prevents future friction wear. Always clear codes with diagnostic software (Dr.EX or equivalent) and perform a test cycle to confirm repair.

---

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and seek qualified diesel technician assistance for complex electrical diagnostics or repairs.