What is Hitachi ZX170W-3 Fault Code P1113 (105-3)?

Fault Code P1113 (105-3) on the Hitachi ZX170W-3 excavator indicates an Intake Air Temperature (IAT) Sensor Circuit High Voltage condition. This code triggers when the Engine Control Module (ECM) detects an abnormally high voltage signal from the intake air temperature sensor, typically reading above 4.5-4.8 volts instead of the normal operating range of 0.5-4.5 volts.

The IAT sensor plays a critical role in the ZX170W-3's Isuzu engine management system by measuring incoming air temperature to optimize fuel injection timing, air-fuel ratio, and combustion efficiency. When this sensor circuit fails, the ECM cannot accurately calculate air density, leading to improper fuel delivery and reduced engine performance. This is particularly problematic in wheeled excavators like the ZX170W-3, where precise engine management is essential for both travel and hydraulic operations.

Common Symptoms

• Engine warning lamp illuminated on the instrument cluster, often with reduced engine power
• Hard starting or rough idle, especially in cold weather conditions
• Black smoke from the exhaust due to overly rich fuel mixture
• Decreased fuel efficiency and noticeable loss of horsepower during operation
• ECM defaulting to a fixed air temperature value (typically around 77°F/25°C), causing poor performance in extreme temperatures

Potential Causes

The most common causes of P1113 in used ZX170W-3 excavators include:

• Open circuit in the IAT sensor wiring harness, often caused by wire chafing near the air intake manifold mounting points
• Failed IAT sensor with internal resistance breakdown (common after 5,000+ operating hours)
• Corroded or damaged connector pins at the sensor plug, frequently caused by moisture infiltration in the engine compartment
• Shorted sensor ground wire creating a high voltage reading to the ECM
• ECM internal fault (rare, but possible in high-hour machines with electrical system issues)

How to Troubleshoot and Fix Code P1113 (105-3)

Step 1: Visual Inspection Locate the IAT sensor on the air intake manifold (integrated into the intake tube near the air filter housing). Inspect the sensor connector for corrosion, bent pins, or moisture. Check the wiring harness for visible damage, particularly where it routes near metal brackets or the exhaust system. On used machines, look for wire insulation cracks or rodent damage.

Step 2: Electrical Testing Disconnect the IAT sensor connector. Using a digital multimeter, measure resistance across the sensor terminals. At 68°F (20°C), resistance should read approximately 2,400-2,700 ohms. If the reading shows infinite resistance (open circuit) or deviates significantly, replace the sensor. Check the harness-side connector for 5-volt reference voltage from the ECM with ignition on.

Step 3: Wiring Harness Verification Perform a continuity test from the sensor connector to the ECM pins (refer to Hitachi service manual for specific pin locations). Check for shorts to power by measuring voltage between sensor signal wire and ground with the sensor disconnected—any reading above 0.2 volts indicates a wiring fault. Inspect grommet entry points into the ECM housing for wire chafing.

Step 4: Component Replacement Replace the IAT sensor with a genuine Hitachi or Isuzu OEM part (aftermarket sensors often cause repeat codes). Apply dielectric grease to connector pins before reassembly. Clear codes using Hitachi Dr.EX diagnostic software or equivalent and perform a test cycle.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi ZX170W-3 service manual and consider professional diagnostic assistance for complex electrical issues. Improper repairs may cause additional damage or safety hazards.