Hello,
I have replaced the cat about 4 months ago and O2 sensor, recently replaced the fuel pump and now it’s pulling the P0420 code. I’ve put more money than it’s worth into this car and I’m not willing to replace the cat again. I JUST replaced the cat so what is the possibility this is the cat again? Is there something I can do to fix this?
how old is this vehicle? what is the model, mileage, and age?
unlikely it was ever the cat in my opinion.
a common cause of P0420 is holes in the exhaust allowing air to leak in and upset the O2 sensor.
get a spray bottle of dish soap and water, jack the car up, spray it while the engine is running and look for holes in the exhaust.
another cause of P0420 is a bad ignition coil.
It is a 2016 nissan versa note S, taking note so show my husband! Thank you! It has around 100k miles
Please tell him this:
On a 7 year old car it is unlikely the CAT or Sensors are faulty and need replacing. Unless there has been some serious neglect and damage.
Some of the most common reasons for P0420 are when the exhaust system after the CAT but before the lambda sensor has leaks from damage or corrosion which lead to air leaking in and upsetting the O2 sensor.
Get eye protection and a spray bottle and spray it with dish soap and water and look for bubbles where the exhaust has leaks.
Exhaust leaks can be repaired by an exhaust repair kit, often using high temperature sealants and clamping or tying metal sheets over the holes.
Another common reason is when ignition plugs or coils fail. Spark plugs are usually rated to well over 50k miles if they are iridium but you should check them.
Ignition coils will cause the engine to either misfire or not properly ignite which will lead to the code. It may be difficult to identify which plug is failing without an error code.
Everything mentioned here are not expensive to purchase and isn’t too difficult of a job to do.
Did you replace the original Cat with an OEM? If it was a cheaper aftermarket unit it is very likely the Cat again, about 50% of the aftermarket Cats I’ve installed on vehicles were insufficient right out of the box. We only recommend installing OEM converters.
My mechanic replaced it, my husband believes it was oem, could there be a more root problem? Like something causing the cat to fail?
Any other codes other than the p0420, I would double check and make sure it was an OEM unit though.
I’ll call the mechanic in the morning, no other codes.
Hope you get this sorted! Let me know how it goes, I’m always curious! Good luck!
-Tyler Nelson
Tyler Nelson Automotive | Guelph, Ontario, Canada
Will do!