Cylinder 3 Injector - Current Above Normal / Short to Ground
What does CAT-INJ3-FMI6 mean?
The CAT-INJ3-FMI6 (Caterpillar) diesel fault code means: Cylinder 3 Injector - Current Above Normal / Short to Ground. This is a serious severity code.
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
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.
Frequently Asked Questions
What does CAT code INJ3-FMI6 mean?
CAT code INJ3-FMI6 (Cylinder 3 Injector - Current Above Normal / Short to Ground) is a serious-severity fault on Caterpillar on-highway diesel engines. This code flags cylinder 3 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 INJ3-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 INJ3-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.