Cylinder 5 Injector - Current Above Normal / Short to Ground
The CAT-INJ5-FMI6 (Caterpillar) diesel fault code means: Cylinder 5 Injector - Current Above Normal / Short to Ground. This is a serious severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- advanced
- Estimated cost
- $400-$1800
Down with a CAT fault on the road?
Get connected with a verified mobile diesel mechanic near you. Verified diesel & reefer techs, launching on the freight corridor.
Find a mobile mechanic →A $30 car code reader can't do diesel. The HD7000 reads full-system codes and does parked DPF regen, idle/speed-limit, and service resets from the cab — on everything from a 6.7 Cummins/Power Stroke/Duramax pickup to Class-8 trucks (Detroit, Paccar, CAT, Volvo, Mack, International).
Full-system 6/9/16-pin diesel scan tool for Cummins, Paccar, CAT, Detroit and more — plug-and-play, no subscription. A cheaper way to read heavy-duty codes a basic OBD2 scanner skips entirely.
Affiliate links — we earn a commission at no extra cost to you.
Common Symptoms
- Check Engine Light
- Injector shutoff on the affected cylinder
- Rough idle and loss of power
- Possible no-start if multiple injectors
Probable Causes (Ranked by Likelihood)
- Injector coil or wire shorted to ground Very Likely
- Chafed wire in rocker box Likely
Frequently Asked Questions
What does CAT code INJ5-FMI6 mean?
CAT code INJ5-FMI6 (Cylinder 5 Injector - Current Above Normal / Short to Ground) is a serious-severity fault on Caterpillar on-highway diesel engines. This code flags cylinder 5 injector fault. CAT on-highway engines use HEUI (hydraulically actuated) injection pre-2007 and common rail post-2007. Confirm with CAT ET cylinder cutout test before replacing a $500-$800 injector. Diagnose with CAT ET (Electronic Technician) software.
Can I drive my truck with CAT code INJ5-FMI6?
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 INJ5-FMI6?
Typical repair is $400-$1800. 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 and run cylinder cutout.
Remove valve cover and inspect injector wiring for pinched wire to ground / rocker arm rub.
Measure injector solenoid resistance to case; any continuity to case indicates injector failure.
Replace injector or repair harness short as found.
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
- Kenworth T800 with CAT C15
- Kenworth W900 with CAT C15
- Kenworth T2000 with CAT C15
- Peterbilt 379 with CAT C15
- Peterbilt 389 with CAT C15
- Peterbilt 386 with CAT C15
- Peterbilt 387 with CAT C15
- Freightliner Classic XL with CAT C15
- International 9200i with CAT C15
- International 9400i with CAT C15
- Western Star 4900 with CAT C15
- Western Star 5900 with CAT C15
- Kenworth T800 with CAT C13
- Kenworth T660 with CAT C13
- Peterbilt 386 with CAT C13
- Peterbilt 387 with CAT C13
- Freightliner Columbia with CAT C13
- International 9200i with CAT C13
Related Codes
Explore More
Was this helpful?
Send this to whoever is fixing the truck — your tech, or the person asking what the fault means.