Sumitomo SH200-5 Fault Code 1173: Technical Guide

What is Sumitomo SH200-5 Fault Code 1173?

Fault Code 1173 on the Sumitomo SH200-5 excavator indicates a malfunction in the engine controller communication circuit or a battery voltage abnormality detected by the ECM (Engine Control Module). This code specifically relates to the power supply system that maintains stable voltage to the electronic control units.

The SH200-5 utilizes a sophisticated electronic control system where the ECM continuously monitors battery voltage and charging system performance. When voltage falls outside the acceptable range (typically below 20V or above 32V for this 24V system), Code 1173 triggers. This is critical because unstable voltage causes erratic sensor readings, improper fuel injection timing, and potential damage to expensive electronic components. On used excavators, this code often emerges due to aging electrical infrastructure that wasn't designed for extended service life.

Common Symptoms

When Code 1173 is active, operators typically experience:

• Engine cranks slowly or struggles to start, especially during cold weather conditions
• Warning lamp illumination on the instrument cluster, sometimes accompanied by reduced engine power
• Intermittent electrical issues such as gauge flickering, display resets, or inconsistent hydraulic response
• ECM may enter limp mode, limiting engine RPM to approximately 1,500 to protect electronic systems
• Battery discharge warning appearing on the monitor panel, even with a relatively new battery

Potential Causes

The most likely technical reasons for Code 1173 on used SH200-5 excavators include:

• Alternator failure or undercharging due to worn brushes, failed diodes, or faulty voltage regulator
• Corroded or loose battery cable connections at terminals, especially the ground connection to the frame
• Deteriorated main power harness between the battery and ECM, common at vibration points near the engine mounts
• Failing batteries that cannot hold proper charge, particularly in machines with original 5+ year-old batteries
• Damaged wiring at known rub points near the swing bearing or along the upper frame rail
• Faulty ECM power supply relay or blown fuses in the main power distribution box

How to Troubleshoot and Fix Code 1173

Step 1: Initial Voltage Assessment Using a quality digital multimeter, measure battery voltage with the engine off (should read 24-26V) and running (should read 26-29V). If running voltage doesn't exceed resting voltage, the charging system has failed.

Step 2: Inspect Battery and Cable Connections Remove both battery cables and inspect for corrosion, fraying, or heat damage. On used excavators, check the main ground strap between engine block and frame—this often corrodes internally while appearing intact externally. Clean all connections with a wire brush and apply dielectric grease.

Step 3: Test Alternator Output With engine at high idle (approximately 2,000 RPM), measure alternator output directly at the alternator terminals. Proper output should be 27-29V. If voltage is low, test the voltage regulator and check alternator belt tension (should deflect no more than 10mm with moderate thumb pressure).

Step 4: Harness Continuity Check Trace the main power harness from batteries to the ECM, checking for voltage drops exceeding 0.5V. Pay special attention to connectors near the hydraulic pump (common vibration zone) and where harnesses pass through the cab floor. Use a test light to verify ground integrity at multiple chassis points.

Step 5: ECM Power Supply Verification Locate the ECM power relay in the fuse box and swap with an identical relay to eliminate relay failure. Check the main ECM fuse (typically 30A) for signs of heat stress or micro-cracks.

For used machines, thoroughly inspect connector pins for backing out, a common issue after years of vibration. Replace any corroded connectors rather than attempting to clean severely oxidized pins.

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Disclaimer: This guide provides general troubleshooting information. Always consult the official Sumitomo service manual and consider professional diagnostic services for complex electrical issues, especially when working with ECM systems that may require proprietary software for complete diagnostics.