What is Hitachi ZX350K-5G Fault Code 20113-2?

Fault Code 20113-2 indicates a malfunction in the Engine Speed Sensor Circuit - specifically an intermittent or erratic signal being received by the Engine Control Module (ECM). This diagnostic trouble code (DTC) is triggered when the ECM detects irregular voltage patterns or signal dropouts from the crankshaft position sensor or engine speed sensor, which monitors engine RPM and crankshaft timing.

On the Hitachi ZX350K-5G excavator, this sensor is critical for proper fuel injection timing, engine synchronization, and overall power management. The Isuzu engine powering this model relies heavily on precise speed data to optimize combustion efficiency and hydraulic system performance. When this signal becomes unreliable, the machine's computer cannot accurately control engine functions, potentially leading to performance degradation or unexpected shutdowns.

Common Symptoms

• Intermittent engine stalling or rough idling, especially during warm-up or under load
• Engine warning lamp illuminated on the instrument cluster with reduced power output
• Erratic tachometer readings or RPM gauge fluctuations during operation
• Difficulty starting the engine, requiring multiple cranking attempts
• Sudden loss of hydraulic power during digging or lifting operations due to engine derate mode

Potential Causes

The most common causes of Code 20113-2 on used ZX350K-5G excavators include:

• Damaged or corroded wiring harness near the engine speed sensor, particularly at known rub points along the engine block where vibration causes wire insulation wear
• Failing crankshaft position sensor due to heat exposure, oil contamination, or internal component degradation common in high-hour machines
• Loose or corroded electrical connectors at the sensor or ECM caused by moisture intrusion or age-related oxidation
• Excessive air gap between the sensor and reluctor wheel due to mounting bolt loosening from engine vibration
• ECM internal circuit issues or corrupted software calibration files (less common but possible in older units)

How to Troubleshoot and Fix Code 20113-2

Step 1: Visual Inspection Begin by inspecting the engine speed sensor located on the flywheel housing. Check for physical damage, oil leaks contaminating the sensor face, and verify the mounting bolts are torqued properly. Examine the entire wiring harness from sensor to ECM for abrasion, melted insulation, or rodent damage—pay special attention to harness routing near hot exhaust components.

Step 2: Electrical Testing Using a digital multimeter, disconnect the sensor connector and measure resistance across the sensor terminals (typically 190-250 ohms for Isuzu sensors, but verify with service manual specifications). Check for voltage supply at the harness connector (should be approximately 8-12V with ignition on). Inspect connector pins for corrosion or bent terminals, which are extremely common in used excavators exposed to harsh environments.

Step 3: Signal Analysis Connect Hitachi diagnostic software (Dr.EX or equivalent) to monitor live sensor data. Observe the frequency signal while cranking the engine—it should show smooth, consistent pulses. Erratic patterns confirm sensor or harness failure. If unavailable, an automotive oscilloscope can verify signal integrity.

Step 4: Replacement and Verification Replace the sensor if readings are out of specification or if physical damage exists. Before installation, clean the reluctor wheel on the flywheel and verify proper air gap (typically 0.5-1.5mm). For used machines, always apply dielectric grease to connectors to prevent future corrosion. Clear codes and perform a test run under load.

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