The short answer
A steady check engine light means your car’s computer logged a fault — anything from a loose gas cap to a failing sensor. If the car runs normally, it’s safe to drive briefly, but get it diagnosed within days: small faults compound into expensive ones, and in New York a lit check engine light is an automatic NYS inspection failure.
Likely causes, ranked
- 01
Oxygen sensor or fuel-trim faults
most commonAging O2 sensors and lean/rich codes are the most common check-engine causes nationwide. Symptoms are subtle — mostly falling MPG — while the catalytic converter quietly absorbs the abuse.
- 02
EVAP leak — including the gas cap
commonThe emissions system that captures fuel vapor is leak-tested by the computer constantly. A worn cap seal, cracked hose, or faulty purge valve sets the light. Sometimes it really is the gas cap.
- 03
Misfires — plugs, coils, or injectors
commonWorn ignition parts cause intermittent misfires that set codes before you feel them. Left alone, they escalate to the flashing-light stage that destroys converters.
- 04
Catalytic converter efficiency (P0420/P0430)
commonOften the end result of an ignored upstream problem. Sometimes it’s a lazy sensor mimicking converter failure — worth verifying before spending four figures.
What to do right now
- 1
Check the gas cap first — tighten until it clicks. If that was it, the light clears itself over a few days of driving.
- 2
Pay attention to how the car runs. Normal = book a diagnosis this week. Rough, down on power, or flashing = stop and call now.
- 3
Skip the parts-store code read → parts-cannon cycle. Codes are symptoms; diagnosis finds causes. Ours is $89–$149 and applies to the repair.
- 4
Inspection sticker due soon? Don’t wait on it. The annual NYS inspection runs an OBD-II emissions test on 1996+ vehicles, and a lit light fails on the spot — fix first, then inspect.
What it typically costs
Diagnosis at Fogg’s is $89–$149, credited toward the repair. Fix costs vary wildly by cause — a $40 gas cap, a $250 sensor, or a converter at $900–$2,400 that proper early diagnosis usually prevents. For fleet accounts we log the code against the unit’s history, so a repeat fault on the same van shows up as a pattern, not a surprise.
Our diagnosis fee goes toward the repair.
Related questions
Can I just clear the code and see if it comes back?
You can — but clearing also erases the freeze-frame data that helps diagnose it, and a recently cleared computer fails the NYS inspection as “not ready” until its emissions monitors have re-run. Better: get it diagnosed, then clear it once it’s actually fixed.
The light has been on for a year and the car runs fine. Do I really need to fix it?
Two problems: an active fault often has the computer running compensations that waste fuel and wear the converter, and the lit light will mask the next fault — the serious one gets no announcement.
Plus it fails the NYS inspection, and the sticker expires on its own schedule, not yours.
Will my car pass the New York State inspection with the check engine light on?
No. For 1996 and newer vehicles under 8,501 lbs, the emissions portion of the annual NYS inspection is an OBD-II scan, and a lit malfunction indicator lamp is an automatic fail.
The $21 state fee is the same either way, so diagnose and repair first, then inspect — we do both in one visit at Fogg’s.
What actually fixes it
If it turns out to need real work, this is what usually does it — with pricing published up front, so there are no surprises.
Same symptom on a work van or truck? Fleet units get priority bays and one monthly invoice. Fleet repair →
Still not sure how serious it is?
This guide describes common patterns, not a diagnosis of your specific vehicle — that takes an inspection. If your symptom is marked urgent, treat it as urgent. When in doubt, stop driving and call (518) 348-7764.
