What is Hyundai R455LC-7 Fault Code 100-4?

Fault Code 100-4 on the Hyundai R455LC-7 excavator indicates an Engine Control Module (ECM) communication error or CAN bus communication failure between the engine controller and the machine's main display system. This diagnostic trouble code (DTC) signals that the Engine Control Module is not receiving or transmitting data properly through the Controller Area Network (CAN) communication line, which is critical for coordinating engine performance, hydraulic functions, and operator interface displays.

This code is particularly significant on the R455LC-7 because this model relies on integrated electronic control systems to manage fuel injection timing, emissions controls, and power output coordination with the hydraulic pump demand. When communication breaks down, the machine cannot optimize performance or may enter limp mode to prevent potential damage, severely limiting productivity on the jobsite.

Common Symptoms

When Code 100-4 is active on your Hyundai R455LC-7, operators typically experience:

• Complete loss of engine data on the main monitor display (no RPM, coolant temperature, or fuel level readings)
• Illuminated warning lights including the check engine light and possibly the master caution indicator
• Engine derate or power reduction as the ECM defaults to safe operating parameters without communication feedback
• Intermittent or complete gauge cluster failure, with displays flickering or going blank entirely
• Inability to access diagnostic menus or perform electronic calibrations through the operator interface

Potential Causes

The most common technical failures triggering Code 100-4 on used R455LC-7 excavators include:

• CAN bus wiring harness damage at known rub points near the engine firewall and behind the left-side service panel where harnesses contact frame members
• Corroded or loose connector pins at the ECM harness connector (C101) or main display connector, especially on machines operated in coastal or high-humidity environments
• Failed termination resistors in the CAN network circuit (typically 120-ohm resistors at network endpoints)
• ECM power supply issues including blown fuses, poor ground connections at G302, or failing main relay
• Software corruption in the ECM or display module, particularly after improper shutdown procedures or voltage spikes during jump-starting

How to Troubleshoot and Fix Code 100-4

Step 1: Perform Visual Harness Inspection Begin by inspecting the CAN bus harness (typically yellow twisted-pair wiring) from the ECM to the main display unit. On used excavators, focus on areas where the harness passes through bulkheads or contacts metal edges. Look for chafed insulation, corroded connectors, or signs of previous repairs with electrical tape. Clean connector C101 at the ECM with electrical contact cleaner and check for bent or recessed pins.

Step 2: Test CAN Network Resistance Disconnect both the ECM connector and the display module connector. Using a digital multimeter, measure resistance between CAN-High and CAN-Low terminals at the ECM harness side. You should read approximately 60 ohms (two 120-ohm termination resistors in parallel). A reading of 120 ohms indicates one missing terminator; infinite resistance suggests an open circuit in the wiring.

Step 3: Verify ECM Power and Ground Circuits Check for proper 12-24V supply voltage at ECM connector Pin 1 (power) with the key switch on. Verify clean ground connection (less than 0.5 ohms resistance to battery negative) at ground point G302 located on the engine block near the ECM mounting bracket. Clean and retighten ground connections, as corrosion buildup is common on machines with 3,000+ operating hours.

Step 4: Check for Software Updates or ECM Replacement If wiring and power circuits test properly, connect Hyundai Hi-MATE diagnostic software or equivalent CAN-compatible scan tool. Attempt to communicate with the ECM directly. If communication fails, the ECM may require reflashing or replacement. For used machines, verify the ECM part number matches the engine serial number range, as mismatched replacement parts from previous repairs can cause persistent communication errors.

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Disclaimer: This guide provides general troubleshooting information for experienced mechanics working on used heavy equipment. Always consult the Hyundai R455LC-7 service manual for model-specific procedures, torque specifications, and safety precautions. If you lack proper diagnostic tools or training, contact a certified Hyundai construction equipment technician to prevent misdiagnosis or further damage to electronic control systems.