VSS OBDII wiring questions.

[dmjensen]

Okay here's the background info: 1992 325i convertible s52 (mid 96) OBDII

I did all the wiring myself no problem, drove it all last summer and when I hooked up INPA to it it gave me a few codes (most are known problems and solutions) but however one was a VSS code.

I figured out on OBDII connector x20 pin #14 is blank (supposedly the vss wire)
I searched for the OBDII way of wiring it on here and found that pin #3 on connector x6031 is the VSS wire.

well that would be fine with most but myself I wanted to verify it in the ETM wiring diagrams. I looked for pin #3 in connector x6031 and back traced it to pin #13 connector x17 (inst cluster) and pin #46 x6000 (dme) both of which say "TI measurement signal (fuel economy)... that doesn't look like VSS to me.. the more I looked I found that pin # 2 connector x17 (inst cluster) is "vehicle speed signal"

can anyone verify or confirm which wire needs to be put to pin #14 C101 for the VSS?

[evandael]

i'm frankly very confused on this issue too.

the speed signal in the e36 diff (x383) goes to the instrument cluster, then to the DME. however, i cannot discern what connectors are in between the cluster and the DME.

here are all the pics i've found in the ETMs..

note x271p4 and x17p2



x271



x17





(^ the above image says that the DME can be found on page 6211.0-03, but it's not on that page)

and finally, on the DME end of it all, the input for the VSS




but frankly I'm confused.. the x6000 only has 88 pins, but it says that the input is on pin 171.


hopefully we can figure this out.

[evandael]

this thread is relevant: http://www.r3vlimited.com/board/showthread.php?t=264748


OP, it appears that even if we find out how to hook up the e30 VSS to the appropriate connector for the e36 DME, it sends a signal at too low of a frequency. this is due to the e30 VSS being based off of the 9-tooth reluctor ring inside the diff, instead how the e36 sees the VSS from the 48-window ABS reluctor ring.

I remember seeing the x20 involved in the ABS circuit.


note x1171p15 and x6000p15


x1171p15


x6000p15



with this information, i'm considering contacting hoveringuy for his Hall-VR convertor circuit. i'll tee off an ABS sensor wire (e30s have 48-window reluctor rings just the same as e36s), condition the signal from the ABS sensor, and send it to the DME via x20p9


this may prove ineffective. it's possible the DME will still need to see the VSS, and only uses the 'speed signal rear' as a means of determining wheelslip for the e36 ASC.

[nando]

the VSS wire is in a 2nd connector next to the X20 on the OBDII harnesses (x6031). It's still a black/white wire. the CEL wire is also in that connector (gray wire).

I'm not sure about the E36 clusters taking a 48 tooth signal. I'm pretty sure they still read off the 9-tooth wheel in the diff - I have an OBDII E36 M3 diff and it has the same sensor/ring as the E30 does.

it wasn't until the E46 that they made that switch, AFAIK.

[dmjensen]

Last time i looked at my x6031 there wasn't a black and white wire at all.

On another note the dme shouldn't be using a wheel speed sensor, it has to be the one in the diff. If your going around a corner on wheel is spinning faster then the other, thus incorrect readings... I'm thinking that 2 x17 isn't the right signal.

Has anyone hooked up their VSS successfully? If so what did you end up doing?

[dmjensen]

Looks like these guys found it. http://www.r3vlimited.com/board/show...ss+obd2&page=3

Only thing is, I want to know if that pin #3 actually is a vss signal or not..

[evandael]

On another note the dme shouldn't be using a wheel speed sensor, it has to be the one in the diff. If your going around a corner on wheel is spinning faster then the other, thus incorrect readings... I'm thinking that 2 x17 isn't the right signal.

that confirms my thought that it's probably a separate signal that the DME compares to the VSS to use for the traction control system.. which we won't be using.


still, it remains worth discussing that the e30 VSS may put out too low frequency of a signal.. for most driving (over 25mph) it does not matter, as the soft-limit doesn't occur due to VSS error and VANOS still actuates. but to have it perfect, i think the signal needs to be modified. i think something inside the e36 cluster steps it up. check out that thread.. it looks like its needs to be multiplied by a factor of 5.333 (9 tooth vs 48 window).


i may still end up investigating the use of a conditioned ABS signal into x6031p3. maybe i'll use one of the front ABS sensors, to avoid wheelspin complications.



EDIT: x6031p3 is a green/red wire in the 1997 ETM. also, it traces back to the DME 'TI fuel consumption' input and comes from the instrument clusters 'TI fuel consumption' output.. ie, not VSS.

[dmjensen]

EDIT: x6031p3 is a green/red wire in the 1997 ETM. also, it traces back to the DME 'TI fuel consumption' input and comes from the instrument clusters 'TI fuel consumption' output.. ie, not VSS.

I know this, that was my original question... I want to know what the TI measurement meaning is. ( fuel economy ) could be a general term they labeled it with, when in reality it is indeed a vss. since there's a label for econometer, which may be different from " fuel economy "


here's my x6031, there is no black and white wire.

pin number 3 is on the right bent downward. green with red tracer.

[evandael]

yeah i know. i just like doing the research so I understand it as well.

my opinion.. there's your red/green. BMW does change wire colors for the same functions, so connect pin 3 to c101 pin 14 and hook it back up to INPA and see if the VSS code goes away.

if not, then that rules out the 'ti measurement' questions.



I'm still curious about the DME VSS input, which is supposedly pin 171. Does anyone know why the ETM says the x6000 connector has over 88 pins? Does it have something to do with CANbus?

[328ijunkie]

There is a VSS signal coming through the X20 on OBD2, its not a bk/white wire like the E30/OBD1 E36. It will work just fine 99% of the time. Its a 1/6 signal to what the ECU is expecting but as long as the ECU sees a signal is some form or fashion it wont code. Seattle circuit sent me a signal converter i still need to install to see if it properly gets the signal at the right hz to be 100% accurate but again the regular signal going through the x20 will work.

[dmjensen]

What pin is it because i went through the ETM several times and can't find anything vss related in the x20 connector?

[dmjensen]

Nevermind, pin # 41 connector x1171 is called a speed signal, which goes to pin #20 connector x20 to the dme.

[nando]

you know, it's pretty trivial to change the K-factor inside the DME to work with the 9-tooth signal. it ends up dropping from ~23,000 pulses/km to about ~4,000.

that would seem to make a lot more sense than special hardware.

[328ijunkie]

^Dont remember off the top of my head if thats right or not but I will hint it doesnt come from the cluster. ;)

[328ijunkie]

Finding that byte is the fun part ;-)