Applicable Systems
EMCP 4.2
Symptoms
The EMCP 4.2 reports fault 268-2 for a Programmed Parameter Fault where the data is erratic, intermittent, or incorrect. This suggests an intermittent connection or noise issue on the parameter circuit rather than a hard short.
Possible Causes
- Loose ECM connector pin causing intermittent parameter data
- Electrical noise on the parameter signal line from nearby high-current circuits
- Corroded ECM ground connection causing reference voltage fluctuations
- Aging EEPROM cell with marginal data retention
Troubleshooting Steps
- Step 1: Check EMCP fault log for intermittent occurrence pattern of 268-2
Fault appears sporadically, not continuously - Step 2: Inspect ECM connector for loose, bent, or corroded pins
All pins straight, clean, and fully seated - Step 3: Verify ECM ground connections are clean and tight
Ground resistance less than 0.1 ohm to battery negative - Step 4: Check for electromagnetic interference sources near parameter wiring
No high-current cables routed parallel to parameter signal wires
How to Reset
To reset: 1) Repair the intermittent connection. 2) Press FAULT RESET on EMCP. 3) Press AUTO.
Frequently Asked Questions
- Q: How is fault 268-2 different from 268-3?
FMI 2 indicates erratic/intermittent data, typically caused by loose connections or noise. FMI 3 indicates voltage above normal or short to power, a more definitive electrical fault.
- Q: Should I replace the ECM for intermittent 268-2 faults?
Only after all wiring and connector inspections have been completed. ECM replacement should be the last resort for intermittent parameter faults.
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Source: Caterpillar EMCP 4.2 Operation & Maintenance Manual (LERMPMM), caterpillarfaultcodes.com CID-FMI Reference
Category: Generator
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