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-   -   Lambda Probe 4, what is this? (http://forum.e46fanatics.com/showthread.php?t=940662)

zhenkaaaM3 08-24-2012 08:27 PM

Lambda Probe 4, what is this?
Scanned an e36 m3 with a code "Lambda probe heating probe 4".

What exactly does this mean?

Thanks in advance.

Zell 08-24-2012 08:29 PM

Isn't a lambda probe an O2 sensor?


They have to heat up to work effectively, so they contain a heating element. This is saying that the heater for it is broken. I'd imagine it is built-in to the sensor and you'd just need a new one.


zhenkaaaM3 08-24-2012 08:36 PM

well ok, do you mind telling me if its post or pre cat?

Zell 08-24-2012 08:41 PM

Well, just from pure guessing, I'm going to assume that 1/2 are pre, and 3/4 are post. It seems like that'd make sense. I'd be surprised if 4 was a pre.

dmax 08-24-2012 08:44 PM

Eugene, I'd be guessing but it sounds like it's be bank 2 and post cat sensor...

But, 02 sensor codes often seem to come about because of other things pretty often...though with only one 02 code (assuming the heater is built into sensor) that might be more reliable.

I do know that cats on an older 750 have heaters independent of the sensor, but don't recall that on an e36.

HTH...good luck!

zhenkaaaM3 08-31-2012 06:29 PM

Can anyone tell me which of the sensors is bad? Location? Post or Pre? Which sensor of the particular location?

and Zell, I have a 99, so would that mean I need this instead?


Oxygen Sensor, fits on CATALYTIC or on MANIFOLD, 990mm, 323i/is/iC (1998-99), 328i/is/iC (1996-99), M3 w/ 3.2L (1996-99), sold individually. NOTE: Each model-year listed requires varying quantity. Please check your car first before ordering.

zhenkaaaM3 08-31-2012 11:51 PM


Zell 08-31-2012 11:57 PM

I know very little about the E36, but I know it is not really all too far off from the E46. If it says you need a specific O2 sensor for a '99 E36 M3, I would trust that.

I do not know exactly which location it is, but I know it is post-cat. If i were you, I'd check E36 forums. If nothing comes up, I'd unplug the wires from the post-cat sensors and see if "Probe 4" comes up for a secondary error (probably something along the lines of 'Lambda Probe (# here) Signal not plausible'). If you get a matching number, then you know just which one it is.

zhenkaaaM3 09-01-2012 09:48 PM

Very smart thinking. I will try that out.

dmax 09-02-2012 06:08 AM

#4 would be the post-cat sensor on bank 2...follow the pipe back from cylinders 4-6...it has to be that one.

zhenkaaaM3 09-02-2012 10:38 AM

Doug, would I need to purchase #2 or #1?

dmax 09-02-2012 11:08 AM


From the diagram, I'd say #2, but that'd be an educated guess...again, post cat sensor, so that's the only one...and that's assuming that's your issue...which does seem likely.

I'd wait for confirmation from someone who isn't guessing, just to be safe!

dmax 09-02-2012 11:09 AM

...and actually, have to add that that realoem diagram was for e46, not the e36 you said you got the code on...so my new answer is 'neither'!

The image, though, should be similar for e36...but the PN is probably different.

zhenkaaaM3 09-02-2012 11:16 AM

then it must be #1 in this diagram. Lambda is aka o2 sensor?

also take a look at this diagram, #15 and #16

dmax 09-02-2012 11:41 AM

#16 would be post cat sensor...so that...not the #1 or the #15...again, on the assumption that the #4 sensor code you got was bank 2 sensor 2...can't imagine it'd be anything else.

Pricey bugger, but I know you can find them for under $100 around.

Also, first I'd make sure that the connections are good. Have you cleared the codes and the same one returned?

jfoj 09-02-2012 12:09 PM

Check fuses first, many of the O2 heater circuits have individual fuses.

If the heaters have individual fuses, you may be able to just pull a fuse to narrow down which O2 sensor is which?

zhenkaaaM3 09-02-2012 01:37 PM

Yes doug. I even cleared it twice to make sure. It popped up right away after i turned car on for the 2nd drive cycle.

zhenkaaaM3 09-06-2012 10:26 PM

Its actually lambda probe heating probe 4. so the heater portion of the sensor I guess malfunctioned. Anyway to fix it without replacing the whole sensor? Maybe add a resistor to it so it gives off "good" readings?

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