What is Hitachi ZX350LCK-5G Fault Code 20113-2?

Fault Code 20113-2 indicates a malfunction in the engine coolant temperature sensor circuit, specifically a voltage signal that is out of the normal operating range or intermittent connection within the engine control module (ECM) monitoring system. This code is triggered when the ECM detects abnormal voltage readings from the coolant temperature sensor, typically indicating the sensor is reporting values outside the expected 0.5-4.5 volt range during engine operation.

For the Hitachi ZX350LCK-5G excavator equipped with the Isuzu engine platform, this fault is critical because the coolant temperature sensor directly influences fuel injection timing, engine protection protocols, and hydraulic oil warm-up sequences. When this sensor fails or provides erratic data, the ECM cannot properly manage engine performance, potentially leading to poor fuel economy, reduced hydraulic efficiency, or unnecessary engine derating to prevent perceived overheating conditions.

Common Symptoms

• Engine warning lamp illuminated on the instrument cluster with reduced engine power output
• Erratic temperature gauge readings that fluctuate rapidly or display unrealistic values (extremely high or low)
• Hard starting conditions when the engine is cold, as the ECM receives incorrect temperature data for fuel mapping
• Premature cooling fan activation or fans running continuously even when the engine is cold
• Reduced hydraulic performance during initial startup due to improper warm-up cycle management

Potential Causes

The most common causes for Code 20113-2 on used ZX350LCK-5G excavators include:

• Corroded or moisture-damaged connector pins at the coolant temperature sensor, especially on machines operating in high-humidity or wet environments
• Damaged sensor wiring harness due to rubbing against the engine block near the thermostat housing—a known wear point on this model
• Failed coolant temperature sensor itself, typically due to internal resistance degradation after 5,000+ operating hours
• ECM ground circuit issues affecting multiple sensor readings, often caused by corroded chassis ground points
• Coolant contamination causing sensor element coating or electrical pathway deterioration
• Previous repair attempts using non-OEM sensors with incorrect resistance curves for the Isuzu engine calibration

How to Troubleshoot and Fix Code 20113-2

Step 1: Visual Inspection and Connector Assessment Begin by locating the coolant temperature sensor on the engine block near the thermostat housing. Disconnect the sensor connector and thoroughly inspect both the sensor pins and harness connector for corrosion, bent pins, or moisture intrusion. On used excavators, this connector often shows green corrosion due to coolant seepage. Clean contacts with electrical contact cleaner and apply dielectric grease before reconnection.

Step 2: Sensor Resistance Testing Using a digital multimeter, measure the sensor's resistance with the engine cold. At approximately 20°C (68°F), resistance should read between 2,000-3,000 ohms depending on exact temperature. Compare your reading against the Hitachi service manual specifications. If resistance is infinite (open circuit) or near zero (short circuit), the sensor has failed and requires replacement. For used machines, also submerge the sensor tip in progressively warmer water while monitoring resistance—it should decrease smoothly without jumping erratically.

Step 3: Wiring Harness and Voltage Supply Check With the sensor disconnected and ignition on (engine off), measure voltage at the harness connector. You should see approximately 5 volts on the signal wire from the ECM. Check for proper ground continuity (less than 1 ohm resistance to chassis ground). Inspect the entire harness run from sensor to ECM, paying special attention to areas where the harness contacts the engine block or frame—common rub-through points on ZX350 models with 3,000+ hours.

Step 4: ECM Parameter Verification If sensor and wiring check out, connect Hitachi Dr.EX diagnostic software or compatible scan tool to verify the ECM is receiving and interpreting signals correctly. Monitor live data for temperature readings while manually warming the sensor. Erratic ECM interpretation despite good sensor function may indicate ECM internal issues or software calibration problems requiring dealer-level diagnostics.

Disclaimer: While this guide provides professional diagnostic procedures, complex electrical issues on construction equipment should be verified by certified Hitachi technicians with proper diagnostic equipment. Always consult the official service manual for your specific machine serial number, as specifications may vary by production year and engine configuration.