Bad O2 sensor

[fastshivy]

1999 540i...
Problem 1
The car is running great; however it sets a code for precat O2 sensor heater on bank 5-8. This occurs about every 300 miles.....clear the code & it pops up again. I replaced both pre cat O2 sensors about 10,000 miles ago because they were setting a code for aging. Immediately after replacing the sensors it set a code for bad O2 sensor on bank 4-8... I then got a new sensor reinstalled it and have had no problems for the last 6 months. I am guessing I just have another bad O2 sensor as this is a different code. It bothers me that it is the same bank every time?? The wiring looks new etc. ...Thought I would check to see if I am missing something here. I only use OEM parts

Problem 2 it set a code for Engine cooling fan control....yet it works fine and does not overheat etc. Any comments here/ Not sure where the control is or how to test it?

[Starmavin]

P0130, p0136, p0150, p0156, p01622. Let me know if you are you gettting any 2 of these codes?

[fastshivy]

Thanks for the response...I am not setting any of the above codes..now here is the scoop...I am using a Peake code reader and here is what it is telling me..

Table OF
Code 05 "PreCat oxygen sensor heater, Cyl#5-8
Now converting hexadecimal to decimal...this gives me a 5..don't what that means except it matches the BMW-FC code for O2 sensor heater circuit (Bank 2 Sensor 1)

Then it gets interesting...The other code it set from table OF is... 8D

The Peake code book says that is an "Engine cooling fan control"....but when you convert it to decimal....it comes out P0155 or O2 sensor heater circuit (Bank 2 Sensor 1) The same thing

I am guessing the table is wrong and I really only have one code Obviously these scanners have no where the capability of a dealer scan...So could this just be the 3rd bad O2 sensor???

[Starmavin]

The reasion is that I remember there being a TSB for o2 sensor codes and cooling system codes that pop up unexplained. The reference number is 12 02 00. It's woth a shot to check while I look into it a little more. While I'm doing that, unplug your DME and main engine connector and look for any funky stuff.

What codes does that scanner bring up, factory FC codes, or obd II codes. If you can go to an advance auto parts store or any where that'll give you a print out of the stored codes before you un plug anything.

[Dirty_Tool]

Most likely you need to have your DME reprogrammed. Depends on your production date but it may fall under SI B12 02 00 as Starmavin mentioned or it also may fall under SI B12 09 02. Either way its most likely a programming issue.

[fastshivy]

Thanks guys..I have not looked at the DME. Will do that today...unless I become a Grandfather! The production date is 10/98 The Peake reader I have uses its own tables and is in a hexadecimal format. I converted the numbers by multiplying the left digit times 16 and adding the right digit to it....This gives the P format so... it really does not directly use any of the codes stated above. There was another thread about 6 months ago I was ranting about the Germans drinking to much beer and Dirty tool suggested the DME that time...funny how things always come back to the original problem!

Looks like a trip to the dealer may be in order....Any guesses on a normal charge for this? I don't use the car everyday so... can the DME be sent off for a reflash?

Again many thanks for your time and efforts

[fastshivy]

Well I just found my post from 08/02/06 It was bank 1-4 I had trouble with before....Damn retard juice and old age! Still may need the reflash???

[Starmavin]

That may expalin the O2 but doesn't explain the cooling system code. Either way I'll need the exact codes.

[fastshivy]

I converted wrong...Here are the exact codes......P0155 and P0141

[CosmosBlack]

If it helps at all...the last time I had codes that read lean/rich mixture in banks 1-4,
I ended up replacing the oil separator, CEL went away but returned to bug after a while.
Then finally, replaced the MAF sensor, that solved the problem.

If you need a good BMW indy mechanic, let me know.
I used to go to Sam's off Beach Blvd. He's the main BMW guy in Jax.
He's also the only indy in town who has the dealer diagnostic software (forgot what it's called) to read all your codes and do programming.

[fastshivy]

Those codes according to Bentley are O2 sensor heater circuit...both banks..fuses are Ok wiring in to ECM looks good..maybe a relay or something? The car runs perfect, but I am going to sell it or trade it for a truck. I don't want the new owner to have any problems.
Forgot about Sam..if I can't figure it out from the forum then i will go there.
replaced the Maf about 7mo ago due to your suggestion and it has been great ever since! thanks again

[Dirty_Tool]

It still needs the reflash. The reflash will widen the parameters at which the O2 sensors will set a fault. As far as the cooling fan fault is concerned I would just check your cooling fan and if it is working ok then it may have been a 1-time deal. Just keep an eye on it and see if it keeps setting the code. If so you may have a fan which is on its way out (motor windings breaking down)

[fastshivy]

Thanks DT good advice!