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Discussion Starter · #1 ·
Hello everybody,

Im new to the forums. I drive a 98 e36 323is and have been having overheating problems lately. My check engine light is lit so i took it to autozone to have them do there free diagnostic check. They came up with the code P0141. Also, on the paper it describes

"Definition
Heated oxygen sensor- Bank 1 Sensor 2 (h02S12) B sensor heater circuit
Explanation
BBOpen or short circuit condition
Probable cause
BB1- Poor electrical connection
BB2- Faulty HO2S12 (bank 1 sensor 2) "

I've had mixed reviews on why my car is overheating. Many people say that my cat is bad and causing exhaust gas buildup in the block and causing the overheating. Others tell me that my O2 sensor is shot and i need to replace it. I also believe it is the O2 sensor, but i would like to be a good amount certian before I go and spend the $120 on a new one. This problem arrised after i had the CAT taken out and welded back in, if that would cause any difference. Any help greatly appriceated.

Thanks and Godbless,

Logan
 

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Discussion Starter · #3 ·
It happens if i drive over .. lets say 8 miles. ever since it happened the first time I started shifting it at lower rpms to try and keep the heat in the block down. it will bog hard if I punch it or try and take off in second (which before i could easily do)

I think it is the O2 sensor failing or something causing it to run rich (I run 91 octane). Which would cause the bogging and overheating I believe. I am not a mechanic though, which is why im coming here so i know more before I buy parts.
 

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Discussion Starter · #8 ·
Okay, so I looked over my hoses and checked all my fluids and everything in that catagory is okay. I think my catalytic converter is clogged though. I started it and revved a few times and there was stuff comming out of my exhaust. It seemed like my cat has clogged and when i rev it hard it spews some of the built up stuff from the cat out.
 

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Discussion Starter · #10 ·
i would look at replacing your cat with a high flow one also how new is your fuel filter? hope the cat issue sorts out your problems but this would be the first time i've heard of a cat causing a car to overheat. keep us posted
I know of a few people who's cat's have caused them to overheat. When the cat is clogged not allowing airflow through the exhaust it gets backed up in the cylinder causing it to bog down and overheat really bad. At least that's what I've heard from people around here.
 

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Your confusing issues; the overheating is coincidental to the cats, sensors and any work you've done or had done on them. Or not. The cooling systems on these cars are good, excellent really, so long as they are maintained. This means changing fluids, thermostats, hoses, pumps, and yes even radiators in a timely fashion. These vehicles, contrary to much ill-informed opinion, do not thrive on neglect nor run forever. Get a Bentley manual, check out the service intervals and start making your plans. Right now it sounds like, maybe, the thermostat. Stop driving the car and overheating it! Order the parts and the manual and fix it. Start with the easy and least expensive. But hey, blow a head gasket/crack the head or block and you're going to be really sorry. Solve the overheating and then tackle the CEL and O2 sensors.
 

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Discussion Starter · #14 ·
so, what do you think would be the best thing to do? Replace the O2 sensor first (since im not 100 percent sure my cat is clogged) and then hopefully that will fix my check engine light. then proceed to replace the cat if needed?

thanks everybody,

logan
 

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"The O2 sensors on an OBD-II car are scheduled to be replaced every 100,000 miles.

Pelicanparts has these for about $108 apiece. They are plug and play. Yes, you can buy "generic" and solder them in, but if they don't work, well, you'll get frustrated fast. For the amount saved in labor, it is worth it to spend a little more on quality parts.

a 22 mm box end wrench can take these out, although they do sell a special tool which is nice.

There are several O2 sensor error messages, and not all of them mean "replace O2 sensor". Most mean something else. There is no "bad oxy sensor" code per se.

OBD II error codes only reveal symptoms, not causes. Even BMW mechanics, though, fall for the "read code and replace named part" error.

These are some of the following messages and possible causes,

1. O2 sensor out of range (or adaptive range limit met): Usually an air leak and the easiest and most common place is the intake elbow after the MAF sensor. A $30 part and ten minutes to replace. This is NOT an O2 sensor problem, usually.

2. Catalytic Converter Efficiency Below Threshold: This appears to be a primary oxygen sensor failure. Not really a failure per se, but merely the sensor wearing out and giving inaccurate readings (going out of calibration). Replacing the primary sensor seems to fix this, although it could also be the catalytic converter being worn out, or the secondary sensor giving an improper reading. Again, the code gives the symptom. The mechanic (you) still has to determine the cause.

3. Heater wire: Open circuit or improper resistance on heater wire. Usually a broken connection to the sensor, a bad sensor, or a disconnected sensor (This is a handy code, as if you get confused as to which sensor plug goes where during installation, just disconnect one and read the code - this error will tell you which sensor you just disconnected).


Use a Peake code reader to get more detailed code readings. The P-code readers used by the auto stores give only vague generic message codes."

RobertPlattBell
 
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