P0420 or P0430 code and a smog failure, or a stolen catalytic converter — we handle both. We diagnose the root cause before recommending cat replacement (misfires, oil burning, and exhaust leaks all trigger P0420 without a failed cat). We don't perform smog certifications — we fix what caused the failure so you can pass at a smog station.
Catalytic converter service in Chico covers two scenarios: a failed cat causing a P0420/P0430 check engine code and failed smog test, or a stolen catalytic converter — increasingly common in Chico and Butte County. We perform pre-smog CEL diagnosis to identify cat failure, exhaust repairs to fix cat-related codes, and catalytic converter replacement with OEM-quality parts. We do not perform smog certifications — we perform the repair so you can pass at a smog station.
P0420 (Bank 1) and P0430 (Bank 2) are the most common catalytic converter codes. They mean the downstream oxygen sensor is detecting that the cat isn't converting exhaust gases efficiently enough. Before condemning the cat, we confirm the code isn't caused by an upstream issue — misfires, oil burning, coolant contamination from a head gasket leak, or a failed oxygen sensor can all trigger P0420/P0430 without a failed cat.
If your vehicle failed smog with a P0420/P0430 code, we diagnose the root cause before recommending cat replacement. A cat that's poisoned by coolant from a head gasket leak needs the head gasket fixed first — replacing the cat without fixing the upstream cause destroys the new cat within months. We fix what caused the failure, then replace the cat if needed.
Catalytic converter theft has increased significantly in Chico and surrounding Butte County communities. Toyota Prius, Honda Element, Ford F-Series, and trucks with high ground clearance are common targets. Signs of theft: loud exhaust roar on startup, check engine light, rattling under the vehicle. We replace stolen cats with OEM-quality parts and can install anti-theft heat shields on vehicles at high risk.
Exhaust leaks upstream of the catalytic converter — cracked manifold, failed manifold gasket, or loose flex pipe — allow unmetered air into the exhaust stream, triggering P0420/P0430 without any cat failure. Exhaust leak repair is often less expensive than cat replacement. We inspect the entire exhaust upstream of the cat before recommending replacement.
Tedious Auto Repair does not perform smog certifications. We perform: pre-smog inspections, CEL diagnosis to identify smog failure causes, exhaust and catalytic converter repairs to fix the failure, and confirmation that the readiness monitors are set before you go to a smog station. After our repairs, take your vehicle to a licensed smog station for certification.
After any catalytic converter or exhaust repair, we confirm that all OBD readiness monitors are complete before you leave. Incomplete readiness monitors (from a recent battery disconnect or repair) will cause a smog failure even if nothing is wrong. We drive the vehicle through the appropriate drive cycle to set the monitors.
P0420 means the downstream oxygen sensor detects the catalytic converter isn't reducing emissions efficiently. Before replacing the cat, confirm the code isn't from a misfire, oil burning, coolant contamination (head gasket), or a failed oxygen sensor — all can trigger P0420 without a failed cat.
Call (530) 826-4275. We replace stolen catalytic converters with OEM-quality parts. We can also install anti-theft shields. Bring any police report number for your records.
No — we don't perform smog certifications. We perform pre-smog inspections, diagnose and repair CEL issues causing smog failures, and confirm OBD readiness monitors are set before you go to a smog station for certification.
Not immediately — OBD readiness monitors need to run after any repair. We drive the vehicle through the appropriate drive cycle to confirm monitors are complete before you go to the smog station. Going with incomplete monitors causes a smog failure.
Depends on vehicle and whether it's Bank 1, Bank 2, or both. Written estimate after diagnosis confirms the cat is the actual failure cause. We never replace a cat based on a code alone — we verify the code is caused by the cat and not an upstream issue.
Free 100-point digital inspection · Written estimates · NAPA Gold 3-year / 36,000-mile warranty
📍 2695 CA-32, Chico, CA 95973 · Open Mon–Fri 7AM–5PM · Sat 8AM–5PM · Sun 9AM–5PM
2695 CA-32, Chico · (530) 826-4275
2695 CA-32, Chico · (530) 826-4275
Buddy Rausch founded Tedious Auto Repair in Chico, CA in 2007 and has been serving Butte County for 18+ years. As an ASE Master Technician, Buddy personally oversees diagnostics and quality control on every vehicle. All content on this page reflects real procedures, OEM specifications, and cases seen in the shop. Learn more about Buddy →