Applicable Systems
PC200 Excavator
Symptoms
ECM power supply voltage fluctuating; intermittent ECM resets; multiple system codes may appear simultaneously.
Possible Causes
- ECM power supply relay contacts worn
- Battery cable corrosion at terminal
- Alternator voltage regulator intermittent
Troubleshooting Steps
- Step 1: Measure battery voltage at engine OFF and ON
12.6V OFF, 13.8-14.4V running - Step 2: Check ECM power relay contacts
Contact resistance < 0.5 ohm - Step 3: Inspect battery terminals for corrosion
Terminals clean and tight - Step 4: Test alternator output stability
Voltage stable +/- 0.2V - Step 5: Replace relay or alternator as needed
Voltage stable at ECM power terminal
How to Reset
Clear via service monitor after power supply repair.
Common Replacement Parts
- ECM Power Relay P/N: 600-66-11110
Frequently Asked Questions
- Q: Can bad battery cause ECM resets?
Yes. If battery voltage drops below 10.5V during cranking or operation, ECM may reset and lose adaptive learned values.
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Source: truckmanualshub.com Komatsu PDF
Category: Heavy Equipment
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