O2 sensor/Catalytic converter problems

[Benjipro5]

Hey guys, I own a 2002 protege5(mj) and my check engine started flashing, so i took it to get diagnosed at autozone and they told me it was something with the catalytic converter or O2 sensors, it has 148,XXX miles on it and i bought it used so im not sure what to do. (eek2)
anyone have the same problem on their Pro5?

any advice would be awesome, thanks.

 

[slavrenz]

My guess is that they pulled two codes - P0300 and P0421.The P0300 is a misfire, which will cause your check engine light to start flashing, as it means damage is being done to the catalytic converter (basically, unburnt fuel is being dumped down your exhaust). If you haven't already, I would replace the spark plugs, plug wires, and ignition coils and see if that helps things. At 148K miles, it's probably way overdue.

As for the P0421, that means that the catalytic converter has been ruined, and you will likely need a new one.

Again, these are guesses - it would be very helpful if you knew those codes that AutoZone pulled from your car.

 

[Megazuel]

The flashing MIL was definatley a misfire code, its the only thing that will falsh a MIL. Egr cleaning, tune up, etc. to get rid of the misfire. As for the "converter code", don't just assume that you need a converter yet. Fix the misfire issue, clear the codes and drive it and let the car set the cat monitor. If it resets a Cat code and there are no O2 codes set, then you can safely assume you need a cat. I wouldn't be surprised with the milage you say is on it. If any O2 codes (lean codes, rich codes, switch time, heater, etc.) set, deal with them first. The cat is the last thing you want to condemn and everything else must be up to par in order for the PCM to properly test it. If you do need a cat, I highly recommend using an OEM unit (yes they are more money) to prevent false cat codes coming back. I still do not trust aftermarket converters, even ones labeled CARB compliant. They are just not the same as OE and the tolerances in testing are so tight, you may wind up still getting efficiency codes with a new "aftermarket" cat.

 

[Benjipro5]

is it worth changing all that or just replacing the exhaust system?(bang)

 

[slavrenz]

is it worth changing all that or just replacing the exhaust system?(bang)

What exactly do you mean? If you change everything, you'll have a new exhaust system anyways. If you are referring to other codes/problems, a new exhaust isn't going to solve them. I agree with the last poster though - deal with everything else before the cat. And try and find out exactly what those codes were so we can help you better.

 

[Diehonda]

Do you have VET testing where you live? If not, get a header and MIL eliminator or nonfouler.

I had this issue a couple years ago and still rocking the header and nonfouler without issues.

 

[Yesmile10]

I have a similar problem, but in the scanner says that has problem with the cylinder 2 and O2 sensor. (Auto Zone)

 

[mechdonald]

I have a similar problem, but in the scanner says that has problem with the cylinder 2 and O2 sensor. (Auto Zone)

Get some new coil packs. They are fairly cheap and quite easy to change and will solve your misfire. Change your plugs and wires while you're at it if they haven't been changed recently.

 

[VP222]

My guess is that they pulled two codes - P0300 and P0421.The P0300 is a misfire, which will cause your check engine light to start flashing, as it means damage is being done to the catalytic converter (basically, unburnt fuel is being dumped down your exhaust). If you haven't already, I would replace the spark plugs, plug wires, and ignition coils and see if that helps things. At 148K miles, it's probably way overdue.

As for the P0421, that means that the catalytic converter has been ruined, and you will likely need a new one.

Again, these are guesses - it would be very helpful if you knew those codes that AutoZone pulled from your car.

I have a same code on my '02 P5. Car has around 132000 miles on it. When code came up previous owner has replaced the spark plugs. But he did not reset the check engine lite. How you reset this lite so I know that there is no more problem. If lite gets reset and does not comes back ON that means there is no further problem ?? My car engine do not have spark plug wires and coil pack (which I used to with my other old cars), but it has small coils on top of each spark plugs. Thanks for any suggestion and advice.

 

[Megazuel]

I have a same code on my '02 P5. Car has around 132000 miles on it. When code came up previous owner has replaced the spark plugs. But he did not reset the check engine lite. How you reset this lite so I know that there is no more problem. If lite gets reset and does not comes back ON that means there is no further problem ?? My car engine do not have spark plug wires and coil pack (which I used to with my other old cars), but it has small coils on top of each spark plugs. Thanks for any suggestion and advice.

How long ago were they replaced and how long have you been driving it with the MIL on? Misfire is constanly checked by the PCM, and after three no fault drive cycles (not three times starting the car), the MIL should go out and the code moves to history until the PCM sees 40 good trips, then dumps it from memory.

The correct way to reset a MIL is with a scan tool. Maybe autozone or a similar parts store would do it for free. Optionally, you could disconnect the positive and negative battery cables and touch them together for 15 -20 seconds, this will reset the entire system including learned fuel trims and the such (radio presets, etc), which is why it isn't the prefered method, but it works. Just unhooking the cables normally doesn't clear everything, as the PCM has capacitors in it that don't drain until you touch the cables together. The car checks for Misfires constantly, so if it doesn't pop right back on after you clear it, problem probably isn't there anymore. Then again, the MIL could be on for other reasons, and without scanning it, you won't know what set it off.

 

[VP222]

previous owner has changed it about 4 months ago. Today I went to one of the local parts store and they shows same code P0300 and something it says catalytic below threshold. He reset the code and car drove fine for about 30 miles and then light came back ON. Car do not have any problem otherwise. Has good power and nothing seems to misfire. I was going to change the spark plug wire and coil pack (as lot of guys has fixed this problem by doing this) but my engine has coils right on top of the plugs. Do you think I can change the boots which seats under this coils!! I have never dealt with this kind of a set up. Thanks for any advice.

 

[Megazuel]

previous owner has changed it about 4 months ago. Today I went to one of the local parts store and they shows same code P0300 and something it says catalytic below threshold. He reset the code and car drove fine for about 30 miles and then light came back ON. Car do not have any problem otherwise. Has good power and nothing seems to misfire. I was going to change the spark plug wire and coil pack (as lot of guys has fixed this problem by doing this) but my engine has coils right on top of the plugs. Do you think I can change the boots which seats under this coils!! I have never dealt with this kind of a set up. Thanks for any advice.

The cat efficiency code (p0420) is probably because the previous owner drove it around with the flashing MIL and flooded the converter with unburnt fuel, which in turn burnt the hell out of the guts of the cat. Either cheat the Cat readings (there is a how-to around here somewhere) or put a new cat on it, but not until you fixed the cause of the problem. Yes, you can get just the boots for the coils, however i just paid 23 bucks a piece for two new coils with new boots, so it may be worth just putting two coils on it.

 

[VP222]

The cat efficiency code (p0420) is probably because the previous owner drove it around with the flashing MIL and flooded the converter with unburnt fuel, which in turn burnt the hell out of the guts of the cat. Either cheat the Cat readings (there is a how-to around here somewhere) or put a new cat on it, but not until you fixed the cause of the problem. Yes, you can get just the boots for the coils, however i just paid 23 bucks a piece for two new coils with new boots, so it may be worth just putting two coils on it.

I checked out the code at auto store and only code is coming up is P0421 "warm up cat efficiency below threshold" That means cat might be bad. My gas mileage in a city is about 26 mpg so I do not think it is O2 sensor. Might plan on changing a cat in a near future.