The catalytic converter is the part that turns the worst of your engine’s exhaust into less harmful gases before it leaves the tailpipe. When it stops working, or when it is no longer on the car, a California smog check is hard to pass. It is also one of the more expensive emissions repairs, which is why drivers tend to look for help the moment a shop says the word “catalytic.”
This guide covers how to confirm the converter is really the problem, what California requires when you replace one, and the help that does and does not exist for the cost.
Signs the Converter Is the Problem
A failing converter usually leaves clues before the test. The car may sound louder than it used to, or rattle from underneath, which can mean the converter’s inside has broken apart. You may notice weaker acceleration or worse fuel economy. The most common sign is a check engine light with a code pointing to catalyst efficiency, such as P0420 or P0430. A lit check engine light will fail the test on its own, as can you pass a smog check with the check engine light on explains.
A sudden roar from the exhaust that starts the same day you notice the car sounds different can mean something else: the converter was stolen. We cover that below.
Why Converters Fail
Converters wear out with age and mileage, but they are also killed by other problems. An engine that misfires or runs rich sends unburned fuel into the converter and can overheat it. A coolant or oil leak into the exhaust can coat it. A hard hit from road debris can crack the inside. Because of this, replacing the converter without fixing the cause can mean a second failure, so the first step after a code is a diagnosis, not a parts order.
Confirm Before You Replace It
A catalyst efficiency code does not always mean the converter itself is bad. A failing oxygen sensor can set the same code, and fixing it costs a fraction of a converter. Ask your repair shop to show how they confirmed the diagnosis, and get the estimate in writing. If your smog check report lists a failed emissions reading, what happens if your smog check fails in California explains how to read it, and top reasons vehicles fail smog tests shows where converters fall among the common causes.
Check Your Warranty First
Before you pay for a converter, find out whether the car is still covered. BAR’s Smog Check Reference Guide notes that catalytic converters fall under the federal emissions warranty for the first eight years or 80,000 miles. If your vehicle is inside that window, the manufacturer may owe you the repair. Call a dealer with your VIN and mileage before you authorize anything. A converter that was replaced recently may also still be under the installer’s own warranty.
California Rules for Replacement Converters
California does not let you bolt on any converter that fits. BAR says a replacement converter must come from the original equipment manufacturer or be a California Air Resources Board (CARB) approved aftermarket converter with an assigned Executive Order number that matches your exact vehicle. A converter that fits the pipes but is not approved for your vehicle is not a valid fix, and a vehicle with the wrong one can fail the inspection.
CARB’s guidance for aftermarket converters adds that the installer must document the reason the converter is being replaced, and that the warranty must be passed to you in writing. CARB’s published guidance gives the aftermarket warranty as five years or 50,000 miles, so ask your installer to confirm what applies today. Read the details in CARB’s guidance on aftermarket converters, or ask your shop which approved part number they are using for your car. BAR says replacement should be done by a licensed Smog Check station, and that it must be completed before your next inspection.
If Your Converter Was Stolen
Converter theft is common because the metals inside are valuable. If yours was stolen, you will usually know right away from the noise, and the car will not pass a smog check until a correct converter is installed.
Here is what to do. Report the theft to the police, since your insurer will ask for the report. Call your insurance company, because some policies cover stolen auto parts. Then arrange for an approved converter to be installed. BAR states plainly that its Consumer Assistance Program does not cover the replacement of a stolen catalytic converter, so do not count on it. BAR’s page on catalytic converter theft and the smog check program is the official reference, and it also points to the manufacturer or BAR’s Smog Check Referee program if your replacement is hard to find.
Help With the Cost After a Failed Test
If the converter failed because of wear or damage, and the car failed its smog check, the Consumer Assistance Program may be able to help. CAP describes its repair assistance as covering emissions-related repairs for income-eligible drivers, and a converter is an emissions repair. BAR’s site does not list a separate converter-only program, so be cautious with any page that claims otherwise. Our guide to the California Consumer Assistance Program lists the current amounts and eligibility rules. Apply and get approved before the repair is done, because work completed beforehand may not qualify.
If the repair is more than the car is worth, retirement is the other CAP option, and the same guide covers it.
After the Repair
Once the new converter is on and any related problem is fixed, the car needs to be retested. Drive normally for a while first, because a repair or a cleared code can leave the car’s emissions monitors not ready, and a car in that state usually cannot be tested. Our guide to what to expect at a smog check explains what the technician checks. If you are retesting at EZ Smog Check, the pass or free re-test applies.
Frequently Asked Questions
Can a bad catalytic converter fail a smog check?
Yes. A failed converter can raise emissions above the limits, and a catalyst code will keep the check engine light on, which fails the test.
Does insurance cover a stolen catalytic converter?
Some policies do. Call your insurer and ask about stolen parts. BAR advises owners to contact their insurance provider.
Does CAP pay for a stolen converter?
No. BAR states that the Consumer Assistance Program does not cover replacement of a stolen catalytic converter.
Can I use any aftermarket converter?
No. It must be an OEM part or a CARB-approved aftermarket converter with an Executive Order number matching your vehicle.
Is there a separate assistance program for catalytic converters?
BAR’s site does not list one. The Consumer Assistance Program covers emissions-related repairs for eligible drivers whose vehicle failed a smog check.
Will a new converter fix my smog check failure?
Only if the converter was the cause. Confirm the diagnosis first, and fix any underlying problem such as a misfire.
Smog Check After a Converter Repair in Torrance
When the repair is done, we can retest your car. We are a STAR-certified station, so we test both regular and STAR-required vehicles. If you are planning ahead, see how much a smog check costs in California.
EZ Smog Check 1719 Abalone Ave UNIT 407, Torrance, CA 90501 Phone: 310-533-1940
Hours: Monday to Friday, 8:00 am to 5:00 pm Saturday, 9:00 am to 4:00 pm
No appointment necessary. Pass or have a free re-test.
