2012 JKU Error Code P0430 & P0304. CAT & Coolant leak?

Moab

Moab

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Looking at a used 2012 JKU. 120k miles and in excellent condition. Other than the below.

1) I'm having a mechanic check it out on Monday. But the owner has been fairly forthcoming about any issues. Its getting error Code P0430, owner says the left bank catalytic converter needs to be replaced due to inefficiency. I've never had cat problems.

Can I use a universal $300 catalytic converter from Autozone? Whats the cheapest I can get this fixed for?

2) It's also throwing code P0304 but it goes away. He says it sometimes looses coolant on very hot days. Does not overheat. And there is no coolant in the oil. But the owner seems to think it has a pinhole headhasket leak. He says it does not affect drivability. And that he's been driving it like this for 5 months. He is getting a new truck delivered this week. So was on the fence about addressing it before he sold it.

When I look up causes for this code. The majority say its a known cylinder head issue. How could my mobile mechanic diagnose this issue? Is there a recall on this? Seems like it could be a major issue. Maybe I should have it inspected at the dealership?

I wouldn't even screw with this. But its it in excellent condition. Very well taken care of. He seems like a straight forward guy. Letting me know known issues without asking. And he's agreed to reduce the price a great deal. Otherwise I would not be able to afford a 2012 with the 3.6 engine. I'd be forced to look at JKUs with the 3.8.

Advice?
 
The dealership can diagnose the 0304 misfire code for $210. But it can be everything from a sparkplug to a cylinder head. Or I guess worse if its caused engine damage. Jeep issued an extension on the manufacturer warranty to 10yrs and 150k. Unfortunately for this vehicle that extension ran out in March.

I'm just wondering if its worth the $210 to have it diagnosed. It runs fine. The Jeep is in excellent condition. Two owner vehcile. And the Carfax is excellent in terms of no damage and lots of dealership services and minor warranty repairs.
 
I just found this. And it says the most likely reason for the P0304 code is a bad catalytic converter. With this Jeep throwing the cat code 0430 and the 0304.

What are the chances the 0304 is cat related and not a bad cylinder head? And what damage may have been caused by this guy driving it for 5 months like this? He does not report any drivability issues though.

https://getjerry.com/car-repair/p-z...ne-code#what-does-the-engine-code-p-0304-mean

"What can cause the P0304 engine code?

The P0304 engine code can be caused by several things, all of which can be serious and require immediate attention. Ultimately, a cylinder misfire can damage your car engine and result in costlier repairs if left unattended.

The main issue caused by misfiring cylinders is damage to the catalytic converter. The catalytic converter’s purpose is an important one as it converts toxic gases and pollutants into less toxic pollutants through the process of catalyzing a redox reaction.

The common causes behind the P0304 engine code include:

Faulty spark plug 4
Clogged or faulty fuel injector 4
Faulty ignition coil 4
Fuel injector 4 circuit poor electrical connection
Ignition coil 4 harness is open or shorted
Ignition coil 4 circuit poor electrical connection
Insufficient cylinder 4 compression
Incorrect fuel pressure
Intake air leak"
 
I can't even spell JKU but since you're in California it'll need to be a CARB (California Air Resources Board) compliant catalytic converter. Maybe Autozone can get that for you but I'd turn down any that are Duralast which is the store brand for Autozone. And yep any of those causes in your last post could be responsible for the misfire. I doubt a bad cat would cause just one cylinder to misfire.
 
Moab said:
Looking at a used 2012 JKU. 120k miles and in excellent condition. Other than the below.

1) I'm having a mechanic check it out on Monday. But the owner has been fairly forthcoming about any issues. Its getting error Code P0430, owner says the left bank catalytic converter needs to be replaced due to inefficiency. I've never had cat problems.

Can I use a universal $300 catalytic converter from Autozone? Whats the cheapest I can get this fixed for?

2) It's also throwing code P0304 but it goes away. He says it sometimes looses coolant on very hot days. Does not overheat. And there is no coolant in the oil. But the owner seems to think it has a pinhole headhasket leak. He says it does not affect drivability. And that he's been driving it like this for 5 months. He is getting a new truck delivered this week. So was on the fence about addressing it before he sold it.

When I look up causes for this code. The majority say its a known cylinder head issue. How could my mobile mechanic diagnose this issue? Is there a recall on this? Seems like it could be a major issue. Maybe I should have it inspected at the dealership?

I wouldn't even screw with this. But its it in excellent condition. Very well taken care of. He seems like a straight forward guy. Letting me know known issues without asking. And he's agreed to reduce the price a great deal. Otherwise I would not be able to afford a 2012 with the 3.6 engine. I'd be forced to look at JKUs with the 3.8.

Advice?
Click to expand...

1) When it comes to replacing the catalytic converter, it's generally recommended to use an OEM or direct-fit replacement rather than a universal one. While universal converters may be cheaper, they may not fit properly or provide the same level of efficiency. As for the cost, it can vary depending on the specific make and model of your vehicle. Getting quotes from different mechanics or shops would give you a better idea of the cost in your area but I can tell you that you're probably going to see a wide variety of costs depending on the parts used as well as the shop.

2) The P0304 code indicates a misfire in cylinder 4, and the coolant loss could be a potential symptom of a leaking head gasket. If you're concerned about the potential for a major issue, it might be worth getting a second opinion from a trusted mechanic who specializes in Jeeps. Make sure that the mechanic does a compression test and a leak down test. Do not buy it without having those tests run first and reporting back with the numbers.

Do NOT but a 3.8 JK. The 4.0 is superior to the 3.8 in every way. The 3.8 is a real turd of an engine.
 
Chris said:
1) When it comes to replacing the catalytic converter, it's generally recommended to use an OEM or direct-fit replacement rather than a universal one. While universal converters may be cheaper, they may not fit properly or provide the same level of efficiency. As for the cost, it can vary depending on the specific make and model of your vehicle. Getting quotes from different mechanics or shops would give you a better idea of the cost in your area but I can tell you that you're probably going to see a wide variety of costs depending on the parts used as well as the shop.

2) The P0304 code indicates a misfire in cylinder 4, and the coolant loss could be a potential symptom of a leaking head gasket. If you're concerned about the potential for a major issue, it might be worth getting a second opinion from a trusted mechanic who specializes in Jeeps. Make sure that the mechanic does a compression test and a leak down test. Do not buy it without having those tests run first and reporting back with the numbers.

Do NOT but a 3.8 JK. The 4.0 is superior to the 3.8 in every way. The 3.8 is a real turd of an engine.
Click to expand...

You mean don't buy a 3.8. But do buy a 3.6 right? Thats why I'm so hot on this 2012. First year of the 3.6.

I saw several recommendations online for Walker cats. But can not find a CARB Walker cat for use in California. Rockauto carries a brand called Eastern that is CARB. But it's $928. Could I use one from a junkyard?

How hard is it to register a Jeep in say NV or AZ if you live in CA? Seriously. A cat is like a $2000+ repair. It would be cheaper to drive to AZ and register it there. If that were possible
 
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Moab said:
You mean don't buy a 3.8. But do buy a 3.6 right? Thats why I'm so hot on this 2012. First year of the 3.6.

I saw several recommendations online for Walker cats. But can not find a CARB Walker cat for use in California. Rockauto carries a brand called Eastern that is CARB. But it's $928. Could I use one from a junkyard?

How hard is it to register a Jeep in say NV or AZ if you live in CA? Seriously. A cat is like a $2000+ repair. It would be cheaper to drive to AZ and register it there. If that were possible
Click to expand...

Correct, avoid the 3.8 like the plague. Going from a 4.0 to a 3.8 is a downgrade. Going from a 4.0 to a 3.6 is an upgrade.

I don't know how the CARB b.s. works but there is no reason you can't use one from a wrecking yard.

Well you need an address to register your vehicle in AZ or NV and not all areas of these states are exempt from emissions. Where I live in Arizona we are fortunate to not have to deal with emissions (thank goodness). Maricopa County however has emissions.

Again though, you need an address in one of these states.
 
So I can get the p0304 code diagnosed at the dealership for $220. But I'm debating whether to even spend the $220 to have it diagnosed. The only California CARB compliant cat is over $2000.

Unless I can use one from a junkyard for around $350. Anyone ever do that?

Second, worse case scenario with the p0304 cyl 4 misfire is a new cylinder head. Does anyone know which side cylinder head that is? And if using a used one from a junkyard is worth it? I have not priced them out yet. Iirc the part is more expensive than the labor. Once I know which side head it is I can price that out. Used and new. But hopefully its just a head gasket or spark plug issue or something more minor.

From what I've researched the p0304 misfire probably caused the cat to go bad. As the owner did not address the p0304 code right away. And as I may have mentioned he missed the manufacturers warranty. Which just expired in March. Big mistake on his part.
 
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