Firestone's diagnostic fee is about $100 in 2026

What changes the diagnostic on a Firestone visit

Firestone's diagnostic is a package, not a code read

Firestone Complete Auto Care sells the diagnostic as a check engine light service: a technician pulls the codes, checks freeze frame data, and tests the circuit or component the code points at, billed as roughly one hour of shop labor. The company's own page says the code is the starting point, not the answer, and the fee buys the testing. That is the right description. What you are not paying for is a factory scan tool; Firestone uses aftermarket equipment, which is fine for the engine and emissions faults that make up most check engine visits.

What Firestone credits and what it does not

Firestone stores generally apply the diagnostic charge toward the repair when you approve the work at the same visit, and treat it as a stand alone charge if you take the car elsewhere. Policies are set per store, so confirm at the counter before authorizing. Firestone also runs a free courtesy check (fluids, belts, tires, battery) that is a visual inspection, not a diagnostic; do not confuse the free check with the paid diagnostic when comparing quotes.

Where it fits

Firestone is a good match for a check engine light on a mainstream car out of warranty, a battery or charging complaint, brakes, and anything tire related. It is a poor match for a car under warranty, a fault in a driver assistance system, or a European luxury make, where the store will often read the code and refer you on. The fee is priced like an independent, the hours are longer than most independents, and there is a store in almost every town.