2004 Nissan Maxima 3.5 SE help? Catalytic Converter?

I keep failing my emissions because my check engine light keeps coming on. I was told that the problem was the catalytic converter rear and needed to buy one for both sides. The problem I am having that I don;t know which Catalytic Converter I should buy. I know without it is causing my car to stutter. Any Ideas on which I should get?

If the Check Engine light is on, there must be a list of code(s)?

Do you have that list of code(s)?


As posted by Tester, first thing is to make sure you actually have a bad cat. There’s lots of problems besides cats that causes stuttering. There are tests shops can do to verify the cat is bad. One test for example is to temporarily bypass the cat and see if the stuttering goes away. If it doesn’t, replacing the cat isn’t going to solve your stuttering problem.

If the cat(s) actually test bad, there are probably strict federal rules about what cat brand & model you are allowed to use as a replacement. It depends on where you live. Suggest you surf over to the Rock Auto website and see which replacement cats they recommend for your car. There’s often some annotation w/each cat saying for which states it is legal. Then you’ll have something to go on at least. Best of luck.

The part I failed was Readiness and the code was DTC3 and yes the check engine light is on

DTC3 sounds like a failure code used by your local testing system. If the check engine light is on there is a fault code in the Powertrain control module and usually results in a vehicle emission test failure. You need to have the fault codes read to begin diagnoses.

Stop by an auto parts store. Many of them will read the codes for free. Post those codes here and we may be able to help.

The codes have the format Pxxxx, e.g. P0420, which is a typical code for a catalyst problem.
Another thing: those codes do not say directly that a particular part is bad.
In this case P0420 says that the converter is not working efficiently.
It could be that the O2 sensors aren’t working properly (but not bad enough to set their own code) or the gases going into the converter aren’t correct (garbage in - garbage out) due to an exhaust leak or other issue.
If there are multiple codes then the lowest number code should be dealt with first, the higher number codes may then go away on their own.
Example: a problem (like a vacuum leak) causing P0171may also trigger P0420.

OP writes …

The part I failed was Readiness

That usually means the battery has been recently disconnected. It’s not really a fault code per se, but simply that the computer is in the process of reinitializing it’s memory after a temporary loss of voltage. Until that process is complete, the emissions testers can’t tell if there’s any emissions failures which have been logged by the engine computer. They’ll usually tell you to come back after a few days of driving.

Yea I got to ask my mechanic what the code was cause I don’t really know yet. All he told me was that I need to buy 2 Catalytic Converters for the rear