P0420 Code
Dealership says cat on bank 1 is bad

2004 f150 fx4 5.4l 3v

I want to replace/fix the CEL instead of turning it off on my edge and putting a bandaid on the issue.

I am going to go with Aftermarket to save 1k bucks.

Which ones do I need to replace?

Both on bank 1?

The front cats on both sides?

the rear cats on both sides?

 

P0420 Code
Dealership says cat on bank 1 is bad

2004 f150 fx4 5.4l 3v

I want to replace/fix the CEL instead of turning it off on my edge and putting a bandaid on the issue.

I am going to go with Aftermarket to save 1k bucks.

Which ones do I need to replace?

Both on bank 1?

The front cats on both sides?

the rear cats on both sides?

 

There's a few ways that you can do this. P0420 is the passenger side. You can have all cats removed and replaced with two of the magnaflow universals that a lot of us have used like 94106, 94136 etc. If you want a direct bolt in kit, Magnaflow makes a nice kit that you can get and it will replace everything


Depending on labor rates and your preferences, the kit might actually be cheaper. The converters now cost around 120-160 for both so depending on labor rates these might be a better option. Also, you'd have less of a chance of leaks since you aren't at the mercy of a shop and if you aren't after a louder exhaust note, best to keep it stock. You can purchase the individual cats for each bank, but again they are welded in so there can't be any leaks. Good luck.

 

Universal factory style versions of our cats:

D/S rear & P/S rear

 

Just so I get what you are saying...

1) I can replace 4 cats with 2 cats? Or I can get a kit that costs 360 per side = 720 total before install?

2) If I buy just two cats, am I getting rid of both cats or just the rear or front?

3) I want to go the cheapest route. The shop said they could do the work for around 100 bucks. 120 two cats +100 install = 220 as opposed to the bolt on 720?

4) Will just getting the two put on throw codes?


ps... I would love a more throaty sound without it being loud like my straight piped dodge. I like the mellow tone my flowmaster gives out, but wouldn't mind putting on high flows instead of stock.

 

you can pm me if u want

 

Which circled (red) cats am I replacing?

 

It's all your preference. You can remove all 4 if you don't have visual cat checks. No no in California lol. I don't know which one of your cats is bad. Usually a good mechanic can check the switch rates of the O2 sensors to see where it's stopping up. As long as the job is done properly there should be no codes

 

Two threads merged. One thread per subject olease, to avoid confusion for posters.

 

They just said its my cat on Bank 1. Should I call and have them justify exactly which one is bad? He had told me I only have 2 cats. I am so confused as to how many I even have!?!? Some people say I 2 cats but 2 precats as well. Some say 2 cats/2 resonators. Some say 4 cats. Some say 2 cats.


WTF?!?!?!?!

I do not live in Cali. I live in Indiana, where they could give two ****s less what is on your exhaust system.

The dealership said if I replace one cat, I need to replace both. What does both entail? Does it mean both on Bank 1? Or both as in Bank 1 cat(s) and Bank 2 cat(s).

 

I'd replace that as well. The more you constipate you system, the more problematic it will be. Since the Flowmaster is a channeled exhaust, your slamming exhaust gases into a wall(s). When you trap gases with a cheap, inferior, power/torque robbing muffler like that, the gases have to find away out somewhere and it's usually upstream if its not tight.

 

I called dealership and they said it was the upstream cat on bank 1. So they said just change the upstream cat on both sides.

So you are telling me my flowmaster 40 series clogged my cat? I've never heard of that. What am I supposed to replace it with?

Could I just take all 4 off and run a setup with only one universal magnaflow on each side like this below?

 

No, not at all lol.

 

Are you past the warranty? Probably are, but you may not be. - Depends. If your within, it's a free fix. Here it is, -

The warranty coverage period for:

Passenger cars, light duty trucks (applies to vehicles up to 8,500 pounds GVWR)

(This is you IF your within).

8 years or 80,000 miles (whichever occurs first) for catalytic converters, electronic engine control unit (ECU), transmission control module (TCM), and any other onboard emissions diagnostic module.

 

I have 94k on the truck, so I am out of luck on that one.