Catalytic Converter Service in San Mateo, CA
P0420 code? Stolen cat? CARB-compliant replacement, cat shields, real diagnosis first — we test before quoting a $1,500 cat.
Catalytic converters are expensive to replace and frequently misdiagnosed. Many shops see a P0420 code and quote a new cat — sometimes correctly, often not. Beacon Auto Care in San Mateo tests pre-cat and post-cat O2 sensor signals, checks for upstream causes (rich-running engine, exhaust leak, bad O2), and only quotes a cat when the cat is the actual problem.
Common Reasons Cats Fail
- Engine running rich for a long time — cooks the substrate
- Internal substrate failure / clogging — restricts exhaust flow
- Physical damage — rocks, road debris, undercarriage hits
- Theft — Prius, RX, Element, Tundra commonly targeted
- Heat damage — from a misfire or oil-burning engine
Stolen Cats — Bay Area Reality
Catalytic converter theft is rampant in San Mateo, San Jose, Daly City, and Oakland. If your car suddenly sounds like a hot rod and the CEL came on, the cat was cut out. We replace with CARB EO-listed aftermarket or OEM, and install a cat shield when applicable to discourage repeat theft.
- Live pre-cat / post-cat O2 data confirms cat efficiency before replacement
- CARB EO-listed parts only — passes California smog
- Cat shield installation available for theft-prone vehicles
- 24-month warranty on parts and labor
Common Questions About Catalytic Converter
Diagnosis, theft replacement, CARB compliance, costs.
How do I know my catalytic converter needs replacement?
Don't replace the cat just because of a P0420 code?
Was my catalytic converter stolen? (Honda, Toyota Prius, Lexus RX)
How much does catalytic converter replacement cost in San Mateo?
Will an aftermarket cat pass California smog?
Related car symptoms
Other symptom? Tap below — or walk through our triage tool .
What San Mateo Drivers Say About Engine Repair
“My 2014 Volvo started misfiring while driving on the 101 during a recent Saturday afternoon. With the Check Engine light flashing, I decided to play it safe and brought it to a…”
— Darryl Heller
Read more“Fixed an electronic issue for $250 that Toyota said would require a full replacement for $3,000. Great service and great prices.”
— Leeza K.
“I had a great experience with this shop. My car was consistently overheating, and I was worried about potential engine damage. They thoroughly inspected it, confirmed the radiator…”
— Asmaa A.
Read more“I needed a very quick diagnosis and exhaust fix with my registration renewal and smog test deadline one business day ahead. Flavio and Mo rose to the occasion and took a genuine…”
— Rocky K.
Read more“Brought my BMW here after 3 other shops diagnose it and failed to fix it or even figure out the problem and Moe was a great help he figured out the issue in no time and fixed it…”
— The King O.
Read more“I highly recommend! I was in the area for a day trip when I noticed my engine light was on. Most car repair shops were closed because it was Saturday afternoon. Luckily, Beacon…”
— Rhonda B.
Read moreP0420 Code? Stolen Cat? Get a Real Answer.
Real diagnosis. CARB-compliant parts. Photos to your phone before quoting.