Cylinder 1 Injector - Current Above Normal / Short to Ground
The CAT-INJ1-FMI6 (Caterpillar) diesel fault code means: Cylinder 1 Injector - Current Above Normal / Short to Ground. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $400-$1800
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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 INJ1-FMI6 mean?
CAT code INJ1-FMI6 (Cylinder 1 Injector - Current Above Normal / Short to Ground) is a serious-severity fault on Caterpillar on-highway diesel engines. This code flags cylinder 1 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 INJ1-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 INJ1-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.
Sources
This page is built from documented references. Verify against your own service info before repair work.