Engine Oil Pressure Sensor - Voltage Below Normal (Short to Low)
The CAT-CID100-FMI4 (Caterpillar) diesel fault code means: Engine Oil Pressure Sensor - Voltage Below Normal (Short to Low). This is a critical severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $150-$500
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Common Symptoms
- Check Engine Light
- Sensor reads opposite extreme on CAT ET
- Possible derate or false operating condition
Probable Causes (Ranked by Likelihood)
- Signal wire shorted to ground Very Likely
- Sensor internally shorted Likely
- Moisture or contamination in connector Possible
Step-by-Step Diagnostic Procedure
Confirm active fault in CAT ET.
Disconnect sensor; if the reading flips to the opposite extreme, the sensor is internally shorted.
If reading stays pinned, measure signal wire to ground with sensor unplugged; a short confirms harness damage.
Repair harness chafe or replace sensor as determined.
Frequently Asked Questions
What does CAT code CID100-FMI4 mean?
CAT code CID100-FMI4 (Engine Oil Pressure Sensor - Voltage Below Normal (Short to Low)) is a critical-severity fault on Caterpillar on-highway diesel engines. CID 100 is the Engine Oil Pressure Sensor, measuring engine oil pressure. FMI 4 (Voltage Below Normal (Short to Low)) indicates the specific fault mode. Use CAT ET to confirm before replacing parts. Diagnose with CAT ET (Electronic Technician) software.
Can I drive my truck with CAT code CID100-FMI4?
Short distances may be acceptable, but running long with this fault risks progressive damage or forced derate. Address promptly.
How much does it cost to fix CAT CID100-FMI4?
Typical repair is $150-$500. Sensor / wiring fixes fall at the low end; injector, HEUI pump, turbo, or aftertreatment work falls at the high end. CAT dealer labor often requires CAT ET for calibration and parameter programming.
Sources
This page is built from documented references. Verify against your own service info before repair work.