8V DC Sensor Supply - Voltage Below Normal (Short to Low)
The CAT-CID274-FMI4 (Caterpillar) diesel fault code means: 8V DC Sensor Supply - Voltage Below Normal (Short to Low). This is a serious severity code.
- Keep driving?
- Short distances only
- 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
Frequently Asked Questions
What does CAT code CID274-FMI4 mean?
CAT code CID274-FMI4 (8V DC Sensor Supply - Voltage Below Normal (Short to Low)) is a serious-severity fault on Caterpillar on-highway diesel engines. CID 274 is the 8V DC Sensor Supply, measuring 8V sensor supply for speed sensors and VGT. 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 CID274-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 CID274-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.
Mechanics Guide Step-by-step diagnosis
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.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
Commonly Affected Vehicles
- Freightliner Classic XL with CAT C15
- Peterbilt 335 with CAT C7
- Peterbilt 386 with CAT C15
- Kenworth T800 with CAT C15
- Western Star 5900 with CAT C15
- Peterbilt 389 with CAT C15
- Peterbilt 387 with CAT C15
- Kenworth T470 with CAT C9
- Kenworth T800 with CAT C13
- Peterbilt 386 with CAT C13
- Thomas / Bluebird school bus with CAT C7
- Peterbilt 387 with CAT C13
- Peterbilt 340 with CAT C9
- Peterbilt 379 with CAT C15
- Kenworth T370 with CAT C7
- Kenworth T660 with CAT C13
- International 9400i with CAT C15
- Kenworth W900 with CAT C15
- Freightliner Columbia with CAT C13
- International 9200i with CAT C13
- International 4300 with CAT C7
- Western Star 4900 with CAT C15
- Freightliner M2 106 with CAT C7
- IC Bus shuttle with CAT C7
- International 9200i with CAT C15
- Kenworth T2000 with CAT C15
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