Check Engine Light

[willcall]

Hi, I searched and found no resolution.
My Check Engine Light came on and my motor runs fine. When I get the Code read where can I find a list of the code Discriptions? I also checked the Gas cap and that was on tight. I recently did a full inspection changing all fluids, Belts, Hoses, Water Pump, Thermostat and Housing, Spark Plugs and Boots. I did not however change the O2 Sensor so I am hoping that is the culprit and thats why I want to find what the Fault Code is when I get it read.

[marinm88]

Its most likely the o2.

Google the code with e36 and it should come up. Thats what I usually do.


OR.

Go to advanced auto dignose it and see what the code is there.

GL

[orangehatter]

What is your code?

[flyfishvt]

who ever reads the codes will be able to tell you what the code is. just remember that a code doesn't always tell you exactly what the cause it. For example: a code telling you that you have an evap leak could be caused by several different things. When you get the code read they might be able to tell you what the problem is. If not just google it.

[willcall]

Got the code read, it is 233 Cat Efficiency Bank 1 and oddly enough I filled my gas right after and my Gas Gage only reads 3/4 full when the tank is full. What can that be?

[Exige]

Looks like an O2 problem. Doesn't the 328 have 2 O2 sensors? Which one did you change?

[willcall]

Have not changed the O2 sensors yet, but I would probably just change both. How would I Reset the Check Engine Light after replacing the O2 sensors

[Exige]

The CEL will turn off by itself, but the code will be stored. Any auto parts store can clear the code for you. You need a code reader.

[jmo69]

328's have 4 o2 sensors, 2 pre and 2 post cat @$100 ea. You might have a bad cat also and those are even more expensive. If it's a bad o2 the code should tell you which one.

[Supered M]

328's have 4 o2 sensors, 2 pre and 2 post cat @$100 ea. You might have a bad cat also and those are even more expensive. If it's a bad o2 the code should tell you which one.

you can get them cheaper than that at oxygensensors.com

[willcall]

Went to Pep Boys and the code that they gave me was 233 Cat Efficiency Bank 1, so I am not sure if it is a O2 Sensor or a Cat. The car does have 135,000 miles on it and the motor is running fine and acceleration is good. If the Cat is plugged the car would have diminished acceleration.

[JDStrickland]

Hi, I searched and found no resolution.
My Check Engine Light came on and my motor runs fine. When I get the Code read where can I find a list of the code Discriptions? I also checked the Gas cap and that was on tight. I recently did a full inspection changing all fluids, Belts, Hoses, Water Pump, Thermostat and Housing, Spark Plugs and Boots. I did not however change the O2 Sensor so I am hoping that is the culprit and thats why I want to find what the Fault Code is when I get it read.

BEFORE YOU DO ANYTHING, buy an OBD II Scan Tool. (you can get a Peake, if you want, but the OBD II should do the trick for the same money and also work on other 1996 and later cars and trucks.)

The Scan Tool plugs into a diagnostic port located along the bottom of the dashboard, generally in the area where your left foot is if you were using the clutch. BMW puts the data port behind a small cover that says OBD II DATA PORT, or words to that effect.

The scan tool will pull the codes that are stored, and reset the computer.

Went to Pep Boys and the code that they gave me was 233 Cat Efficiency Bank 1, so I am not sure if it is a O2 Sensor or a Cat. The car does have 135,000 miles on it and the motor is running fine and acceleration is good. If the Cat is plugged the car would have diminished acceleration.

The proper convention for the codes is P0nnn, or P1nnn for powertrain problems. P0 codes are referred to as generic codes, the P1 codes are BMW specific.

You absolutely have two pre-CAT sensors, but if you have one CAT,then you only have one post-CAT sensor.

Bank 1 is the exhaust pipe that includes Cylinder 1, 2, and 3, Bank 2 is the pipe that contains Cylinder 4, 5, and 6. Sensor 1 is the pre-CAT sensor, Sensor 2 is the post CAT sensor. Bank 1, Sensor 2 would be the after-CAT sensor that services Cylinder 1.

Went to Pep Boys and the code that they gave me was 233 Cat Efficiency Bank 1, so I am not sure if it is a O2 Sensor or a Cat. The car does have 135,000 miles on it and the motor is running fine and acceleration is good. If the Cat is plugged the car would have diminished acceleration.

The proper convention for the codes is P0nnn, or P1nnn for powertrain problems. P0 codes are referred to as generic codes, the P1 codes are BMW specific.

You absolutely have two pre-CAT sensors, but if you have one CAT,then you only have one post-CAT sensor.

Bank 1 is the exhaust pipe that includes Cylinder 1, 2, and 3, Bank 2 is the pipe that contains Cylinder 4, 5, and 6. Sensor 1 is the pre-CAT sensor, Sensor 2 is the post CAT sensor. Bank 1, Sensor 2 would be the after-CAT sensor that services Cylinder 1.

Went to Pep Boys and the code that they gave me was 233 Cat Efficiency Bank 1, so I am not sure if it is a O2 Sensor or a Cat. The car does have 135,000 miles on it and the motor is running fine and acceleration is good. If the Cat is plugged the car would have diminished acceleration.

The proper convention for the codes is P0nnn, or P1nnn for powertrain problems. P0 codes are referred to as generic codes, the P1 codes are BMW specific.

You absolutely have two pre-CAT sensors, but if you have one CAT,then you only have one post-CAT sensor.

Bank 1 is the exhaust pipe that includes Cylinder 1, 2, and 3, Bank 2 is the pipe that contains Cylinder 4, 5, and 6. Sensor 1 is the pre-CAT sensor, Sensor 2 is the post CAT sensor. Bank 1, Sensor 2 would be the after-CAT sensor that services Cylinder 1.

[heifetz17]

You absolutely have two pre-CAT sensors, but if you have one CAT,then you only have one post-CAT sensor.

All 6 cylinder e36s have two cats. OBD-II e36s have 4 02 sensors.

I agree that you should definately look in to getting a code reader. However, just to put your mind at ease about the possibility of a bad cat, just take your car to an exhaust shop. They can test the cats and tell you if they're bad or not. Maybe get a couple of opinions just to make sure someone's not trying to yank your chain.

[orangehatter]

All 6 cylinder e36s have two cats. OBD-II e36s have 4 02 sensors.

328i/is/ic M52B28:
-2 cats
-4 O2 sensors

323is/ic M52B25:
-1 cat
-3 O2 sensors

[flyfishvt]

All 6 cylinder e36s have two cats. OBD-II e36s have 4 02 sensors.

Not true. OBDI cars hae only 1 o2 sensor. Its located before the cat. Since we are discussing an OBDII car here I will forgive you.

[JDStrickland]

The OBD I Inline 6 engine has 1 sensor located before the CAT, the 4 has two sensors, one before and one after.

The OBD II Inline 6 has 4 sensors, two before and two after. (That is a bit of a misnomer, the OBD II Inline 6 has two CATs, one sensor before and after each of them.)

[heifetz17]

Not true. OBDI cars hae only 1 o2 sensor. Its located before the cat. Since we are discussing an OBDII car here I will forgive you.

Thanks for the "forgiveness". If you'll read my post, I said all OBD-II cars have 4 02 sensors. I said nothing about OBD-I.

I suppose I should rephrase what I said, though. All 328s have two cats. I wasn't thinking of the 323s!

[orangehatter]

328i/is/ic (Note the two O2 sensor holes after the cats)


323i/is/ic (Note the single O2 sensor before the single cat. There are two on the exhaust manifold)


SO FOR THE SECOND TIME, NO, NOT ALL M52 INLINE SIXES USE 4 O2 SENSORS!

[JDStrickland]

The pic you have for the 323 is the same one that my Bentley manual uses for the M50 motor. I've got a Bentley manual for my E46 cars too, but it hasn't got the same pictures, so I don't know if there is a difference in the M52 from pre-99 and post 99 production. I can't imagine why an OBD II motor would not have a post-CAT sensor because the after CAT inspection of the exhaust gasses is a big part of the change from OBD I to OBD II.

In any case, the OP has a 328, to the configuration of the 323 is a moot point.

[dozanti]

My e36 has one cat, 2 oxygen sensors. Most 323s are this way. Some do however have one oxygen sensor in each manifold and one after the cat, making 3 total

[JDStrickland]

My e36 has one cat, 2 oxygen sensors. Most 323s are this way. Some do however have one oxygen sensor in each manifold and one after the cat, making 3 total

I beleive you are mistaken. OBD II requires an after CAT sensor for each before CAT sensor. The Before CAT sensor adjusts the fuel mixture and the After CAT sensor checks that the CAT is working and the changes called for by the Before CAT sensor are being made.

I don't think the OBD II spec allows for two exhaust manifolds to feed into one CAT. I believe that if there are two manifolds, there has to be a sensor on each, and they have to feed into separate CATs, and the CATs have to have separate sensors.

OBD I allows for a single sensor on a multi-manifold exhaust system, but OBD II does not allow this.

OBD II requires for stricter measuring and monitoring of the exhaust stream, and having two pre-CAT sensors and one post-CAT sensor does not comply with the stricter specification.

Having said all of that, if there is an application of dual manifolds feeding a single CAT, there would only be one sensor after the CAT. I just don't think such a configuration would comply with OBD II, but I could be wrong.

[dozanti]

I beleive you are mistaken. OBD II requires an after CAT sensor for each before CAT sensor. The Before CAT sensor adjusts the fuel mixture and the After CAT sensor checks that the CAT is working and the changes called for by the Before CAT sensor are being made.

I don't think the OBD II spec allows for two exhaust manifolds to feed into one CAT. I believe that if there are two manifolds, there has to be a sensor on each, and they have to feed into separate CATs, and the CATs have to have separate sensors.

OBD I allows for a single sensor on a multi-manifold exhaust system, but OBD II does not allow this.

OBD II requires for stricter measuring and monitoring of the exhaust stream, and having two pre-CAT sensors and one post-CAT sensor does not comply with the stricter specification.

Having said all of that, if there is an application of dual manifolds feeding a single CAT, there would only be one sensor after the CAT. I just don't think such a configuration would comply with OBD II, but I could be wrong.

I only haveone cat, and only two oxygen sensors on the car ........ its a 323is OBDII

[willcall]

Several of the auto shops I have spoken to tell me that the cat itself is going bad and that one cat needs be replaced with an OBDII cat. I have found a shop that will do it for 250 and that includes doing a full diagnostic to make sure the cat is the problem and not the O2 sensor. The dealer wants $277 just for the O2 sensor but allready know I can get a Bosch sensor from the parts store for $104. I have learned that the sensors last around 100k miles and my car has 135k miles on it so I am at odds on what exactley to do?

Would Getting an engine Diagnostic study differentiate between a bad O2 sensor and or a bad Cat?