What is Hitachi ZX350H-5G Fault Code 20113-2?

Fault Code 20113-2 on the Hitachi ZX350H-5G excavator indicates a Hydraulic Oil Temperature Sensor Circuit High Voltage condition. This diagnostic trouble code (DTC) is triggered when the Engine Control Module (ECM) or Hydraulic Control Unit detects an abnormally high voltage signal from the hydraulic oil temperature sensor, typically exceeding 4.8-5.0 volts.

This fault code specifically monitors the hydraulic system's thermal management circuit. The hydraulic oil temperature sensor provides critical data to the machine's control system, allowing it to adjust hydraulic pump output, activate cooling fans, and prevent overheating damage to expensive hydraulic components. On the ZX350H-5G, this sensor is typically located in the hydraulic oil tank or main return line, feeding real-time temperature data to optimize performance and protect the system from thermal degradation.

Common Symptoms

When fault code 20113-2 is active, operators typically experience:

• Warning lamp illumination on the instrument cluster, often accompanied by a hydraulic temperature warning icon
• Reduced hydraulic performance or automatic derate mode, limiting machine speed and digging force to prevent perceived overheating
• Inaccurate or maxed-out temperature gauge readings (often showing constant high temperature regardless of actual conditions)
• Cooling fan running continuously at high speed, even during cold starts or low-load operations
• Stored fault code in ECM memory, retrievable via diagnostic software or panel display

Potential Causes

The most common technical causes for code 20113-2 on used ZX350H-5G excavators include:

• Open circuit in sensor wiring harness, often caused by chafing against the hydraulic tank mounting brackets or frame rails (known wear point on this model)
• Failed hydraulic oil temperature sensor with internal open circuit or degraded thermistor element
• Corroded or damaged connector pins at the sensor plug or ECM harness connection
• Damaged sensor ground circuit or poor chassis ground connection
• Shorted signal wire creating a direct path to battery voltage
• ECM internal fault (rare, but possible in high-hour used machines with electrical system history)

How to Troubleshoot and Fix Code 20113-2

Step 1: Visual Inspection and Connector Check Begin by locating the hydraulic oil temperature sensor on the hydraulic reservoir. Disconnect the sensor connector and carefully inspect both the sensor pins and harness connector for corrosion, bent pins, oil contamination, or moisture intrusion. On used excavators, this connector often accumulates debris and hydraulic oil mist. Clean with electrical contact cleaner and check for physical damage.

Step 2: Sensor Resistance Testing Using a digital multimeter (DMM), measure the resistance across the sensor terminals with the sensor at ambient temperature. Compare readings to Hitachi specifications (typically 200-500 ohms at 20°C, varying with temperature). An infinite resistance reading (open circuit) confirms sensor failure. Also check sensor resistance while gently flexing the connector—erratic readings indicate internal sensor damage.

Step 3: Wiring Harness Voltage Check With the sensor disconnected and ignition key ON (engine off), measure voltage at the harness connector signal wire. You should see approximately 5.0 volts reference voltage from the ECM. If voltage reads battery voltage (12-24V) or fluctuates significantly, inspect the wiring harness from sensor to ECM for damage, particularly where it routes near the hydraulic tank and along the frame rail—a common rub-through point on ZX350H models.

Step 4: Ground Circuit Verification Check continuity between the sensor ground wire and chassis ground. Resistance should be less than 1 ohm. Poor grounds are extremely common in used excavators due to corrosion at ground termination points. Clean and retighten ground connections at the hydraulic tank mounting area.

Step 5: Component Replacement and Verification If sensor and wiring check out, replace the hydraulic oil temperature sensor with a genuine Hitachi or OEM-equivalent part. After installation, clear the fault code using diagnostic software (Hitachi Dr.EX or compatible scan tool) and operate the machine through normal temperature ranges to verify proper sensor function and code elimination.

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Disclaimer: This guide provides general troubleshooting information for experienced technicians. Always consult the official Hitachi ZX350H-5G service manual for complete specifications, safety procedures, and model-specific diagnostic routines. If unfamiliar with electrical diagnostics or hydraulic systems, consult a certified Hitachi technician to prevent equipment damage or personal injury.