Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Catalytic emission


I have a 2006 Dodge caravan. It only has 58, 000 miles. It is in great condition and keep it maintained on a regular basis. Today after getting approximately 20 miles outside of town the check engine light came. The van continued to drive well and run smoothly. I stopped and checked the gas cap and that was fine. When I got back in town I took to my mechanic and he ran a code search on it and found out that the catalytic emission control sensor was possibly going bad ( I think that is what he called it I know he said catalytic emission). He told me immediately to take it to a Dodge dealer because there was a 8 year / 80,000 mile warranty which should cover the fixing or replacement of it. It should also cover labor. I took it to the Dealer and they said they would have to run the code and get documentation but it would be 75.00 just to run the code and if there is a problem it would be applied to the cost or waived. After made an appointment for Monday and left the dealer, the light eventually went off. I recreated what caused the light to come on but to no avail. My mechanic said that the code would be stored. Can some one attest to the warranty and what this problem means? Thank you much.

What people would have to know is what the actual error code was. There is no “catalytic emission control sensor” and even if there was the info you have would be ambiguous without an actual error code.

That said, my best guess is that it was a code suggesting an issue with the catalytic converter - which an emissions reduction device. Its also the case that if your converter is bad it should be covered by that 8/80K warranty.

Your problem is that there are no codes that can tell you that you cat is bad - only ones that suggest the cat might be bad. Getting the codes isn’t a diagnosis - its where you start for diagnosis. So you could go to the dealer & they could get the code, but then tell you its an exhaust leak and not covered by any kind of warranty (cha-ching $$).

Anyway, for most codes the first thing to do is just clear them and see if they come back. If they don’t come back then you just chalk it up to random weirdness and move on.

Do not go to the dealer without your check engine light on. They will tell you “no codes = no problem. Tell us if the light comes back on. That will be $75 please.” So for now if the light is off then forget about it.

Thank you. My mechanic said just what you said now…which now I remember. Are codes stored in the computer memory? Also, will this affect gas mileage if the converter is bad? Is there anything I should worry about other than the check engine light coming on which my mechanic said it probably will at some point. Also, how can I trust the dealer in this small town? I am heading to Michigan next weekend which is about a 7 hour drive? If the light comes on during the trip should I go to a dealer or just wait until I return home three days later?

Yup, codes are stored in the computer memory.
If the code is simply something like P0420 catalyst efficiency below threshold, than the car will run fine and without affecting your gas mileage…but your early warning system, which is what your CEL is, will then be unable to warn you of any other problems. If the code is indicating a bad upstream oxygen sensor, than your gas mileage will probably be affected.

A code indicates that one of the many sensors detected that some erroneous reading. Typically, if you clear the code it will ultimately reoccur. Whatever caused it to trip still exists until it’s repaired. Many times people do get a code that gets cleared and seems to have been an anomolie, but in truth it’ll either disappear completely because they then do a tuneup or something of that nature or it reappears again when conditions are again right.

I’m stepping “out on a limb” saying this without knowing the actual code, but it sounds based on what you’ve said like you should be safe for the trip home.

The codes are stored until they are cleared. Then they’re just gone.

Treat dealers like any other kind of business. Sometimes you can trust them and sometimes you can’t. Ask around your area.

If you head out on the road and the light comes on steady there is normally nothing to worry about. If the light is flashing then you stop driving immediately. If it just comes on steady and the van is behaving normally then just keep on chooglin’ - although you can also go to most any auto parts chain store b/c many of them read the codes for free. You can then get the code & post it for comments.

Thank you again. I called the dealer back and talked to him and he said waiting till the light comes back on is the best thing to do and that was after I talked to you guys…but did not mention that I was on your site…just wanted to see what they would say. I also told him that I did not want to be taken for ride and he assured me that they will not cheat and be honest with me. I did forget to mention that when the light was on it just “seemed” that my gas gauge went down a little quicker, but it could be my imagine. I guess next time I should ask for the code from my mechanic, which he said go right over to the dealer and told me about the warranty…he did not have to think about it…he knew right away when he saw the code. Thanks for everything.

Thanks for the idea of posting the code for discussion. Thanks again for everything. I will look for the check engine light to flash if it gets serious. Have a good weekend and Easter. Enjoy some chocolate this weekend.

Hello again,

I went to Autozone and got the code for the problem. The man there was very helpful. There was another man (I will call him a backyard mechanic) who was very knowledgeable. The code came back PO420 which means it could be the catalytic converter. After much discussion it was decided that this could be an isolated misfire (I think that is what they called it, or, a misread). After starting the car three times and running it for over 50 miles since yesterday, the check engine light has yet to stay on at the starting of the car or while driving it. It seems to be running smoothly and quietly. Can you speak further about the code given at the top? The man from Autozone and the backyard mechanic seemed to think I did not have anything to worry about other than if the light flashes on the high way to and from Michigan, to make sure I pull over and get a code read and get it checked. Thanks…o by the way, both men did think that if there was something wrong, it could be an easy fix.

Here is a nice write up of what that code means and what kinds of things ought to be checked out:

I suppose “easy” is a relative term. The “easiest” fix would be if the converter is bad - because that means Dodge should replace it for free under warranty.

Its true that its not the kind of thing that should interfere with the trip to MI, especially if the light stays off. So I would take the trip without worry. As noted, a flashing engine light would change that. But if a converter problem was really bad you would know it already in how the van runs - they can get clogged and then the engine can’t “breathe” so you would start to notice loss of power under load (like accelerating hard or going up hills).

Thanks much. Have a great Easter and enjoy some chocolate. You guys do a great work. Keep it up.

P0420 is a cat converter code. Your vehicle will run fine as-is and you can make your trip home without worry.

All that code is telling you is that the oxygen sensor has determined that the cat converter isn’t cleaning the exhaust as effectively as the feds would like. The engine couldn’t care less that the converter isn’t doing its thing. The engine has already done IT’S thing by the time the converter gets the exhaust to clean.

Thank you for the info…appreciate it.

Sometimes it’s the rear oxygen sensor (that’s what is generating the code and making the light come on) or it could be the CAT failing.

But FOR sure, the dealer will not do any free repairs unless you drive in with that light on and their diagnostics show a failed part…As long as the light clears itself, the vehicle will pass an emissions test and the emissions warranty is satisfied…

If you are at all concerned about the state of health of either your catalytic converter or your oxygen sensors,or just where your car is running in regards to fuel trim codes all these parts can be checked even if there is not a illuminated “check engine” light.

Of most importance is if the catalytic converter throws a code and it is proven to be accurate and this code indicates your catalytic converter is operating below efficiency AND the 8 yr 80,000 mile warranty has expired. Does Dodge indicate that any grace period will be extended as you previously has a code that said at minimum the efficiency of the cat. or the monitoring system should be subjected to some level of diagnosis but now that minimum level indicator has disappeared.

In short,if the cat. turns up bad at 80,0001 miles are you going to be out of luck?

I see you do have a bit of time with this as your mileage is only 58,000