What is Hitachi ZX870-5A Fault Code 20113-2?

Fault Code 20113-2 on the Hitachi ZX870-5A indicates a malfunction in the Engine Speed Sensor Circuit, specifically a signal abnormality or intermittent connection issue. This diagnostic trouble code (DTC) is triggered when the Electronic Control Module (ECM) detects an irregular or missing signal from the engine speed sensor (also called crankshaft position sensor), which monitors rotational speed and timing for proper fuel injection and engine performance.

This code is critical for the ZX870-5A because the engine speed sensor provides real-time data essential for the common rail fuel injection system to operate efficiently. Without accurate speed readings, the ECM cannot properly control injection timing, leading to poor combustion, power loss, or even engine shutdown protection modes.

Common Symptoms

• Engine warning light illuminated on the operator display panel
• Reduced engine power or derate mode activated, limiting machine performance to protect components
• Rough idling or intermittent engine stalling, especially during cold starts
• Difficulty starting the engine or extended cranking times before ignition
• Erratic RPM readings on the instrument cluster or complete loss of RPM display

Potential Causes

The most common technical reasons for Code 20113-2 on used ZX870-5A excavators include:

• Damaged or corroded sensor wiring harness, particularly at flex points near the engine block where vibration causes insulation wear
• Faulty engine speed sensor due to internal component degradation or contamination from metal debris
• Loose or corroded electrical connectors at the sensor or ECM connection points
• ECM software glitches or outdated firmware requiring reprogramming
• Broken sensor mounting bracket causing excessive sensor gap or misalignment with the crankshaft reluctor wheel
• Water intrusion into connector seals, common in machines with high operating hours in wet conditions

How to Troubleshoot and Fix Code 20113-2

Step 1: Visual Inspection Begin by inspecting the engine speed sensor located on the flywheel housing near the crankshaft. Check for physical damage, oil contamination, or metal shavings on the sensor tip. Examine the wiring harness from sensor to ECM for abrasion, cuts, or burn marks—pay special attention to areas where the harness contacts the frame or engine block.

Step 2: Electrical Testing Using a digital multimeter, test the sensor's resistance (typically 500-1500 ohms, consult service manual for exact specifications). Check for continuity in the wiring harness and ensure no short circuits to ground. Inspect all connector pins for corrosion, bent terminals, or moisture—clean with electrical contact cleaner if necessary.

Step 3: Sensor Gap Verification Measure the air gap between the sensor tip and reluctor wheel teeth using feeler gauges (standard gap: 0.5-1.2mm). Adjust mounting if necessary. On used excavators, verify the reluctor wheel isn't damaged or missing teeth from years of operation.

Step 4: Component Replacement and ECM Reset If testing confirms sensor failure, replace with an OEM Hitachi speed sensor to ensure proper signal characteristics. After replacement, clear fault codes using Hitachi Dr.EX diagnostic software or compatible scan tool, then perform a test run under load to verify repair.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific serial number and consider professional diagnostic assistance for complex electrical issues.