Applicable Systems
EMCP 4.2
Symptoms
Multiple system warning lights flicker; intermittent system faults; ECM may reset unexpectedly.
Possible Causes
- Battery voltage below 12.6V at rest
- Main relay contacts burned/pitted
- Battery cable corrosion at terminals
Troubleshooting Steps
- Step 1: Measure battery voltage with engine OFF (should be >=12.6V)
Voltage >= 12.6V DC - Step 2: Check battery terminal connections for corrosion
Terminals clean and tight - Step 3: Test main power relay contacts for resistance
Contact resistance < 0.5 ohm - Step 4: Replace main relay if contacts burned
New relay contact resistance < 0.5 ohm - Step 5: Verify charging system output (13.8-14.4V at idle)
Charging voltage within spec
How to Reset
Clear all ECM codes with Cat ET after battery/relay service and key cycle.
Common Replacement Parts
- Main Power Relay P/N: 122-5360
- Battery Cable Kit
Frequently Asked Questions
- Q: Can low battery cause multiple fault codes?
Yes. Low battery voltage can trigger multiple false ECM codes across systems. Always check battery first.
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Source: baijiahao.baidu.com Cat 323D code list
Category: Heavy Equipment
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