Skip the auto shop - Our mechanics make house calls

Q: Should I replace or clean the catalytic converter?

asked by on

I was told I have a bad catalytic converter my car is not displaying any of the symptoms of bad converters but the engine check light is on so should I try a cat cleaner first?

My car has 165000 miles.
My car has an automatic transmission.

Hey there. The Check Engine Light can set if the catalyst efficiency is below threshold. There will be no visible symptoms at all, or change in engine performance, because the recorded "low efficiency" can simply mean that more pollutants are being emitted in the exhaust rather than destroyed or "converted" in the catalyst.

So to perceive a difference you would need a gas analyzer to measure what is going on with the tailpipe emissions. Before trying a catalytic cleaner (which itself is problematic if you have a particular product in mind, ask the manufacturer if they have any written, independent laboratory test evidence that it actually works. If they have nothing in hand to send to you, don’t waste your money), the pre- and post-O2 sensors have to be tested in order to determine whether the catalyst has really failed. There is a specific test strategy using output from those two sensors that has to be employed; an exhaust gas analysis is useful as well. If you need help having this checked, a certified professional from YourMechanic can come to your car’s location to diagnose the car and can replace the catalytic converter if necessary.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Won't start. Just cranks, catches, and dies

Hello there, a few different faults will cause your 2001 Pontiac Grand Am to start and then die. Replacing the battery was a good start, as it can cause this type of issues. Other possible faults include the MAF sensor,...

Q: Vehicle shutting off after a loud squeal.

Based on your description I believe you could be having one of two things happening. One explanation of your squealing noise could be a slipping serpentine belt. This belt drives all the accessories attached to your engine such as your...

Q: Performance issues when driving and idling, RPM dropping abruptly

The symptoms you are describing are almost always caused by a bad catalytic converter. When this fails it clogs the exhaust, which causes these problems to occur. Do a back pressure test on the exhaust first. If that is fine...

Related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.