O2 sensors for '97 328

You can get replacement sensors from just about any well stocked parts store. You can get them without the BMW dedicated connector for approximately $50-70 or with the connector for around $100.00 a piece. If yours have never been replaced it is a past due maintenance item. The general consensus is about 100K miles before replacement but they do deteriorate with time. They can be tough to remove but a little heating from a torch works wonders.

RJD

NAPA will sell you some with the BMW connector, or some without the BMW connector. If you buy the ones without the connector, solder and use heatshrink on the wires chopped off of the old sensor. Don't even think about using crimp connectors. If you use the ones with the connector already on, they will cost twice as much but save you some time.

--scott

And, it is likely that the only ones that need to be replaced are those upstream from the converter. The exhaust gas is quite a bit cooler after it leaves the converter. But, of course, a converter expert should realize this. Jim

The CODE tells you which sensor is flaky.

There is a code for each Bank 1, Sensors 1 & 2, and for each, Bank 2, Sensors 1 & 2.

Bank 1 Sensor 1 is the bank that contains exhaust from Cylinder 1, Bank 1 Sensor 2 contains the exhaust from the other three cylinders. Bank 2, Sensor

1 is the CAT that has processed exhaust from the pipe that contains exhaust from Cylinder 1, Bank 2, Sensor 2 is the CAT that contains exhaust from the other three cylilnders.

The CODE will tell you specifically which sensor is tossing up an error. Give us the Code you are getting, and we can tell you which sensor is toast.

You can extract the code(s) with a OBD II scan tool, there is no need for any specialized BMW tools. The OBD II data port lives along the bottom edge of the dash board, either clearly visible OR hidden behind a small cover that is clearly marked -- I believe BMW puts the port behind a small cover and marks it as the data port. (The OBD II spec. requires the data port to be easy to find, so you do not need to spend more than about 5 seconds looking for it. Start your search near where your left leg rests while you are driving.)

The Code for the Bank 1 sensors can be MALFUNCTION, TOO RICH, or TOO THIN, (3 separate codes, one for each condition) or a Code related to the failure of a heater that lives inside of the sensor itself. I forget the Code options for the Bank 2 sensors, but they will translate to the CAT being ineffective. There is a chance the CAT is dead, but a far better chance that the sensor is bad. I have never had a CAT go bad in all my years of driving cars with CATs in them. That is not to say that a CAT can not fail because they can, but it is rare and under normal circumstances the owner/operator of the vehicle has introduced fuel that is not suitable. (One must search out unsutiable fuel, so the odds of this are very low and the effect is very rapid so you would remember the event it it occurred.)

There can be multiple codes for any sensor, so a problem can percolate through the computer in different ways. If you have a code for Bank 1 Sensor

1 and Bank 2 Sensor 2, odds favor only one of them being bad, and the other reporting an out of spec condition that comes from the first in the stream not working right. If Bank 1 Sensor 1 mis-detects the fuel mixture, and adjusts the Fuel Injector Timing to cause more or less fule to be delivered, the result can be that what flows past Bank 1 Sensor 2 is out of spec. In this instance Bank 1 Sensor 2 is okay, and only Bank 1 Sensor 1 is giving you trouble. If Bank 2 Sensor 1 (or Sensor 2) is throwing a fault in isolation, then the sensors at Bank 1, Sensor 1 and 2 are working okay and do not need attention.

Basically, replace the sensor closest to the engine (as the exhaust flows) first to see if it resolves a false report from the next sensor downstream. If the downstream sensor is throwing a code, but the upstream sensor is not, then do not replace the upstream sensor.

What Scott said ....

The caveat being, spend the money and buy a sensor with the connector already attached. The single biggest reason for failure of a repair like this is that the splice job went south. Do yourself a favor and buy the sensor with the connector attached at the factory. I like the Bosch sensors, by the way.

Jeff, Sorry for not snippin' any of your reply, but I didn't want to miss quote anything. I think I followed most of what you wrote except for the second paragraph about Bank/sensor/cylinder relationship. It appears to me that you are talkin' about a 4 cylinder (318) rather than the 6 in my 328. Am I correct or have I misunderstood?

If it's any help the codes it's throwin' are as follows:

233 = Cat. sys efficiency Bank 1 202 = Lambda control stop Bank 1 203 = Lambda control stop Bank 2 234 = Cat. sys efficiency Bank 2

I appreciate all of you folks quick replies, help, & training. Thank You!

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Jinks ('86FXRS, '07 FLTR) #64 Remember, "No good deed goes unpunished"

You can also approach the replacement as a phased effort. The sensors upstream of the converter are the more important and when they fail, your ECU will tend to overrichen the fuel mixture and impact mileage. Replace them first, reset the OBD and see if that solves all or most of your problems. If not, then pursue the rear pair.

R / John

I think you misunderstood. The exhaust header/manifold is split, there are two sets of three tubes that collect the exhaust from the cylinders. Bank 1 Sensor 1 is mounted to the exhaust manifold that connects to Cyl #1. I don't recall which other cylinders it connects to, but it really doesn't matter for this discussion. Bank 1 Sensor 1 sniffs the exhaust coming from the portion of the exhaust that contains Cyl. 1, Bank 2 Sensor 2 sniffs exhaust that comes from the remaining bank. (Bank is a poor term because the motor is an inline and Bank generally refers to the cylinder heads on a V-motor. Having said that, bank is all we have, and the exhaust manifold is split so that it collects from two sets of three cylinders so the term works, if a bit inelegant.)

Proper etiquette is to give the full code, P0233, P0202, P0203, P0234. In the instance where the codes are all in the same family, you can use the shorthand, P0202, 203, 233, and 234. You did okay, but there could be a P1202, and then your use of only the last 3 digits could be misleading.

I'm not sure where you got your information from, but the codes you gave me are completely different from the description.

Try this link,

Given this information -- which I think is wrong but for the sake of example, I'm going to go with it for the moment -- I would replace something upstream from the sensors. Frankly, I'm not sure what to replace, but here is my theory.

The CAT effeciency codes say that the crap coming out of the CAT is not within spec, therefore the CAT is bad or the sensors are bad. BUT, the Lambda sensors up stream are also reporting the contenst of the exhaust as being out of spec. This means that the crap GOING INTO the CAT is beyond what the CAT can deal with, therefore the crap coming out of the CAT is reasonably dirty, and any report of being dirty is understandable. The sensors AFTER the CAT make an assumption about what should come out based on that which went in. But, what went in was more than the CAT can clean, so the reoprt that what comes out is dirty is actually a good report. Bottom line here is that you should not need to replace the CAT or the sensors that are mounted downstream. Your issue is entirely upstream from the CATs.

The Codes P0202 and P0203 are telling you that the fuel mixture is out of spec, I assume TOO RICH, and can't be made any leaner through adjustments that the computer is able to affect -- the computer can adjust the Injector ON Time to affect a change to the air/fuel mixture, but due to reasons elsewhere in the system, the computer can't do its job properly and the P0202 & 203 reports are simply telling you this.

My guess is that your O2 Sensors, all 4 of them, are actually working right, and something in the Fuel Delivery System is running amok causing a TOO RICH condition that the sensors are properly reporting.

Conversely, you could have a vacuum leak that is causing a TOO LEAN condition, but I would not expect TOO LEAN to be something the After CAT O2 Sensors would care about -- if the mixture was lean, then it would lack fuel and therefore it would be clean by definition, and the CAT should be reported as working well; which is cause to not report a Code.

I think you have a TOO RICH condition that is properly reported by the Codes P0202 and P0203, and the resulting exhaust stream that exits the CAT is also TOO RICH and the P0233 and P0234 codes are also accurate.

Having said all of that, review the link I gave you because the codes you supplied should iron out to INJECTOR MALFUNCTION on #2 and #3 cylilnders, and the P0233 and P0234 codes indicate some kind of Fuel Pump problem and an Overboost Condition from the turbo charger, respectively.

I agree with John, but the OP says that both upstream sensors are bad, and this sets off the alarms in my head. It is possible for both sensors to fail at the same time, but I'd be thinking that there is something that is common to them from the perspective of the rest of the system that is setting them off.

My theory on this one is that the sensors are properly reporting a condition that is out of spec, and that there is a repair needed other than replacing the sensors. Having said that, a '97 should need new stuff about now ...

Yeah, some misunderstanding. I know the motor configuration & the split manifold system, I just wasn't sure about your discription.

I got the codes from the report provided by the second shop I had diagnose the problem. That's the way they put 'em on the report. The BMW dealer didn't give me anything, just said "the light is bad cat. converters, & a few other things. We'll do it all for between $3500 & $4000". I decided a second opinion wouldn't hurt. As it stands I have ordered 4 new O2 sensors & arranged to have the other repairs done. Total at that point will be around $700. If it's still throwin' cat. converter codes I can get those replaced for about $500. Total of around $1200 for a good runnin' 11yr old car with 160,000 on the clock. Since I haven't made a car payment in over 7 years I don't mind the cost, but I do want to keep it reasonable. You're right about the upstreem problems & those will be looked into before I consider the converters. Thanks for the help & the link! Usenet is a great place to go for real life experience & info you can't get commercially.

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Jinks ('86FXRS, '07 FLTR) #64 Remember, "No good deed goes unpunished"

Your car is OBD II (On Board Diagnostics, Level 2) compliant, this means you can visit Autozone and they have a standard scan tool that will pull the codes and put them in a format that matches the link I sent you. Autozone does this for free. For the cost of having the dealership pull codes, you can buy the scan tool and pull them for yourself.

The codes you gave me earlier are not OBD II codes, OR they are OBD II codes and the problem is not the Oxygen sensors. The codes you gave me are not sensor codes, they are something else. They could be BMW internal codes, but in any case you do not need CATs or after-CAT sensors.

To know what you need, you need to pull the codes from the OBD II data port. NOBODY (that's n-o-b-o-d-y) should ever attempt to diagnose a problem on your car without pulling the OBD II codes. If you look along the bottom of the dashboard where your knee rests while you drive, you will find either an exposed data port or a concealed port behind a cover that is clearly marked. You do not have to hunt for the data port, the specification requires it to be easily found, and within a few inches of being in the same place on every car and truck from the 1996 model year and newer. Further more, the data that comes out is standardized so that dolts like me can fix their own car if they are so inclined.

I think you are getting ready to throw good money at a problem that isn't. Or, the problem really is, but is diffferent than you think. This means you will be throwing good money after bad ...

Go to Autozone and pull the codes for free. Then spend the money ...