Oxygen sensor test with out lifting the car

[Alpinewhite]

Hi All,

Is there a procedure to test oxygen sensors with out lifting the car.

Thanks
Arun

[92E34]

Are you pulling a code?

[Alpinewhite]

Are you pulling a code?
Yes the code is lambda code 1212. I know it does not directly point to Oxygen sensors but neverthless I want to eliminate oxygen sensors by checking and making sure it does not mal function.

Thanks
Arun

[Russell]

I hope the following is related to this thread.
I get conflicting information on replacing sensors. Only replace when there is a code? replace at 100,000 miles?, or replace at 60,000 miles?. One school of thought is to replace a bit early as they get "lazy" which affects gas mileage and performance.

Mine has been in for 77,000 miles and gas mileage has perhaps dropped 1 mpg. There were no codes last time I checked with my Peak.

Any thoughts?

[bigtisas]

I would like to know too. I am only getting 20mpg for my 92 525ia with 70highway/30city driving.

[92E34]

I used to work in a repair shop. On the wall from bosch it said: Replace Heated O2 sensors (4 wire) every 100,000 miles.

As for the O2 sensor removal without lifting the car...well...forget it. I'll look through my books to see where it comes out so you can test it. The other thing you can do Alpinewhite, is park your car over a ditch or find a place somewhere that you have enough room to crawl under the car.

[bigtisas]

Search the net. You'll find info on testing the oxy sensor. Basically, you need a electronic scope and set it to continuous mode and measure the changing resistance from the oxy sensor while the engine is running. You should see a wave form. Regular ohm meter won't work.

[BillionPa]

do it every 60K

they do get lazy as they age, and if you have any iffy fuel problems like a blown fpr, leaky injector, horrible vacuum leak, they will age faster.

if you have had issues like that in the past, they could already be affecting the sensor output.

if your sensors were replaced and you still get that code, it could be the heater relay for the sensors or a vacuum leak, or failing fpr, failing pump, bad MAF, etc etc...

[trumpetr]

do it every 60K

they do get lazy as they age, and if you have any iffy fuel problems like a blown fpr, leaky injector, horrible vacuum leak, they will age faster.

if you have had issues like that in the past, they could already be affecting the sensor output.

if your sensors were replaced and you still get that code, it could be the heater relay for the sensors or a vacuum leak, or failing fpr, failing pump, bad MAF, etc etc...

Good question. So, can a lazy o2 sensor cause intermittant hesitation and surging at say around 2000-2500 rpm, (no other symptoms,- good idle) without throwing a code?
My car,,,95 525, 81k.

[BillionPa]

yes, it can change the effective fuel mapping, although your car probably has VANOS and the pressure unit could cause that when failing. usually it wouldnt be so intermittent if it was the O2 sensor.

[shogun]

Yes, easy, just remove the plastic from the cover of the ECU and find the right pin where the oxy sensor is. Then use a DMM and you can read while engine is running. You can even put the DMM inside the car with long cables and watch it while driving. Pin depends on the ECU of course.
So in case of the E32 735 built 09/1989
DMM plus on Pin 28, and minus on Pin 10. Start engine, indication should be between 0 and 0,9 Volt, which changes depending on accell.

Study the pinout of your ECU.

[Alpinewhite]

Thanks Shogun. Where will I get the pin out diagram for my car?

Thanks
Arun

[shogun]

Well, for my car I have it here and it shows clearly which pins
http://www.e38.org/e32/750ilpinout1988_90.pdf
Then I have something about MOTRONIC 1.3
http://www.e38.org/e32/m1_3.pdf

If no one has the details, you have to do the work and check the wiring diagrams, takes some hours maybe, but reading the wiring diagrams is the final solution, they are online to be found on this board.
Unfortunately I do not know which MOTRONIC is installed in your model.