I would run the codes first, if it says the sensors are bad then I would replace those first. My 2003 only has one cat in the system.

 

There is only one catalytic converter. There are two oxygen sensors. Well, the front one is probably better referred to as the air fuel ratio sensor.

I agree with @rudyrov, i would see what the code is first. Lots of things cause check engine lights, who knows? Maybe it’s unrelated to your cat.

 

If you want to clear the check engine light then best to find out what Diagnostic Trouble Code (DTCs) are making the check engine light turn on. Then fix it. Otherwise, you are only guessing. Guessing and throwing the parts canon at the trouble can and will cost you lots of money. Get a code reader or bring to auto parts store and get it checked out. Write the codes down and look them up on the internet. Find out what they mean and what the conditions are that cause the light to come on. Fix accordingly.

 

Update (Cat)

OK, so it must’ve gone through it drive cycles;
To recap; I had a brand new catalytic converter put on on account of a check engine light and it throwing what my mechanic said was most likely the cat.

Check engine light was off now it came back on. Then it went off. Now, It came back on.
Note: this is subject to change as I will keep updating until I resolve it

I am going to pull codes possibly later today.

I will drive it another hundred miles and if the light stays on, then I am told it possibly could be the manifold.

hopefully, I will know from the codes, but just trying to get ahead of this, has anybody replaced the cat and then had the vehicle go through its cycles and the check engine light come back on and have remedied it by replacing the manifold?(or perhaps even a donut gasket?) I keep Parts in the garage and have a donut gasket, and can get (whatever manifold or manifold part) before I take it to the mechanic and will just be charged labor instead of labor and parts which saves me some money. This is why I ask.

Been working on cars since I was five but not these CRV‘s. Don’t have the time anymore to do any of the “heavy lifting” time consuming fixes like this would be.

Thanks in advance

 

I’ve seen numerous people on the forum report a repeat p0420 shortly after installing EPA rated cats. Some folk using CARB rated cats report later failures.

 

UPDATE #2
I am wondering if anybody has ever experienced the check engine light going on and off. This is what I am experiencing now after putting on a new cat.
So to recap, we put a new catalytic converter on. Shut the check engine light off. Check engine light came back on. Then it went off. Then it came back on. Then it went off again. And now I’ve lost track because it’s a fleet vehicle and I don’t drive it all the time.
My mechanic is saying it’s something by the manifold. I’ve been around cars since I was five and never really had to deal with cat converters that much but have dealt with them a little bit. This is definitely a first for me check engine light on and off after a brand new cat?
I should mention that I know there’s a drive cycle and it has to go through a couple of them meaning maybe two? This has gone through more than that I’m sure. And while we’re on the subject, what exactly is a drive cycle? How many times you start it and shut it off in a certain amount of time?
My mechanic said to drive it 100 miles. Again, we own a service company and it being a fleet vehicle, it’s driven every day during the week from morning till night. Definitely more than 100 miles.
So the check engine light on and off and on and off and on and off and on and off after a brand new new catalytic converter…

Time to pull codes again I guess.

Insanity

 

There are like 6 or 7 different emissions tests that the second Gen crv runs. Each of the emissions tests needs certain engine criteria before it starts the test (such as a specific coolant temp, rpm, vehicle speed, open/closed throttle etc). The criteria for each test are documented in the service manual if you want to know specifics. After the car runs the test, the drive cycle for that particular emissions test is done.

The emissions tests are either pass, fail, or incomplete which can be seen on a scan tool. The CEL comes on when one of the tests fails.

 

I would have started with what the DTCs are and what conditions are needed to set the check engine light. Don't tell me that the mechanic got a DTC and it said something like P420 cat below efficiency. So, the code mentioned the cat and he replaced it? This is where my headaches comes in. Okay, cat at first turned off the CEL and now it is back , .. at least for the moment.

Is this a federal cat or is it a CARB compliant cat? If federal then can use almost any cat. Carb compliant cats are much more expensive. If spending the money for it then hopefully it is a good one. (The garage probably guarantee the part??).

If the O2 sensors are not OEM then that can cause the CEL issue. I hear it all the time to use the OEM because the Hondas are electronics sensitive. But, who knows??