Four Corners Union

Yes. Four Corners Union is STAR certified with the California Bureau of Automotive Repair, so it can test vehicles the DMV directs to a STAR station, including gross polluters.

No. Four Corners Union is licensed as a Test & Repair station. This station can run your smog test and, if the vehicle fails, diagnose and repair it in the same shop.

Four Corners Union is open Monday 12 AM to 12 PM; Tuesday 12 AM to 12 PM; Wednesday 12 AM to 12 PM; Thursday 12 AM to 12 PM; Friday 12 AM to 12 PM; Saturday 12 AM to 12 PM; Sunday 12 AM to 12 PM. Hours can change on holidays, so call ahead if you are cutting it close.

Yes. Four Corners Union accepts walk-ins, so you can drive in without booking ahead.

Four Corners Union accepts Credit Card, Debit Card, NFC/Contactless.

Google lists the following accessibility features at Four Corners Union: wheelchair accessible restroom.

Four Corners Union has held a BAR smog license since 2004. You can verify the license status at bar.ca.gov.

Four Corners Union has not published a price on SmogCheckDeals. The Bureau of Automotive Repair puts the statewide average at $69.16 as of August 2026, about $65 for a 2000-or-newer vehicle and $73 for 1999-or-older, plus the $8.25 certificate fee. Call (925) 682-3142 for a quote.

Four Corners Union does not take online bookings here, but walk-ins are welcome. Call (925) 682-3142 to check the wait.

Staff at Four Corners Union speak English.

Bring the car, your registration or DMV renewal notice, and a way to pay. Most smog checks take 15 to 30 minutes, and most visits are closer to 20.

Because Four Corners Union is a Test & Repair station, it can diagnose and repair the problem in the same shop, then run the free retest within 30 days. If the repair bill is steep, California's Consumer Assistance Program covers up to $1,200 of emissions repairs for qualifying owners.

The closest alternatives in Concord are Concord Smog Tune & Brakes (0.4 mi) and Faster Auto Repair (0.5 mi). Both are listed further up this page with their ratings and hours.