What is Hitachi ZX870-5A Fault Code 14104-2?

Fault Code 14104-2 on the Hitachi ZX870-5A excavator indicates a malfunction in the Engine Control Module (ECM) power supply circuit, specifically a voltage irregularity or interruption in the primary power feed to the engine's electronic control system. This diagnostic trouble code (DTC) is triggered when the ECM detects that incoming voltage falls outside the acceptable range (typically below 18V or above 32V in the 24V system) or experiences intermittent power loss.

This fault is critical because the ECM serves as the brain of the ZX870-5A's Isuzu engine, managing fuel injection timing, turbocharger control, and emissions systems. Any power supply disruption can cause erratic engine behavior, forced derates, or complete shutdown to prevent catastrophic damage. In used excavators, this code often surfaces due to aging electrical infrastructure rather than ECM failure itself.

Common Symptoms

• Engine derate mode activated, limiting machine to 70% power output or lower RPM ceiling
• Multiple warning lights illuminating simultaneously on the instrument cluster, including check engine and electrical system alerts
• Intermittent engine stalling or failure to start, particularly after the machine has been sitting or during cold starts
• Erratic tachometer readings or complete gauge cluster malfunction
• Loss of electronic functions such as automatic idle shutdown or monitoring system displays

Potential Causes

The most common technical causes for Code 14104-2 in used ZX870-5A excavators include:

• Battery terminal corrosion or loose connections causing voltage drops under load
• Main power harness degradation at flex points near the engine mount or turntable bearing, common failure area for this model
• Alternator output issues – aging alternators may not maintain consistent voltage during high electrical demand
• Corroded ECM power connector pins (particularly the 58-pin main harness connector behind the right-side access panel)
• Damaged main fuse or fusible link in the power distribution box
• Ground strap deterioration between engine block and chassis frame

How to Troubleshoot and Fix Code 14104-2

Step 1: Perform Voltage Testing Using a digital multimeter, check battery voltage with the engine off (should read 24-26V) and running (should read 26-28V). Test voltage at the ECM connector pin 1 and pin 2 while cranking – voltage drop exceeding 2V indicates resistance in the circuit.

Step 2: Inspect All Power Supply Components Physically examine the main power harness from batteries to ECM, focusing on wear points where the harness passes through the chassis. On used excavators, check for harness chafing against the turntable ring gear housing (known wear point). Remove and clean all battery terminals and ground connections with electrical contact cleaner.

Step 3: Test Alternator Output Under Load With engine running at 1800 RPM, activate hydraulic functions and work lights simultaneously while monitoring voltage. Output should remain above 26V. Check alternator mounting bolts for tightness, as vibration-loosened alternators create intermittent charging.

Step 4: Connector Deep Inspection Disconnect the ECM main connector and inspect for green corrosion (common in machines operating in humid or coastal environments). Use dielectric grease on all pins during reassembly. For persistent issues, use Hitachi Dr.EX diagnostic software to monitor real-time voltage while wiggling suspect harness sections.

Disclaimer: This guide provides general troubleshooting information. Always consult the official Hitachi service manual for your specific machine serial number and consider professional diagnosis for complex electrical issues. Improper electrical work can damage expensive ECM components.