E30 obd2 vss

[alndks]

I have an e30 with m52 and the stock e36 dme and harness.
I can see live data from obd2 port with bluetooth adapter and torque app on android phone.
The dme reads very low speed. When i go 15km/h the dme see 2.5km/h, in 30km/h see 5km/h, in 60km/h see 10km/h, in 120km/h see 20km/h.
The problem is in traffic (stop and go) the dme does not get any speed and the vss error appears.
I know this difference is because the m52 dme wants to see speed from abs/dsc with 48 pulse and i give signal from speedometer with 9 pulse, thats why i get 5.3 time less signal.
Is there any way to make the right signal for dme?
I try the signal from the e30 rear wheel abs sensor but it does not work.

[nando]

is it an M52 from a car other than the E36? AFAIK all E36's use a 9 pulse input. on the E46 from what I can tell the ABS computer actually outputs a 10 pulse signal to the DME and cluster, not a 48 pulse, but I've never tested the M52 DME out of an E46.

[alndks]

Its from e36.
The speed signal wire from the dme is brown-red and the manual say that is connect to abs/asc module (speed signal right rear)
And the speed i get from dme (live data) is very very low (120/km/h real speed and the dme see 20km/h)
How i can correct this?

[nando]

that is odd because I input a 9-pulse signal into an E46 DME and the speed was only about 10% lower than expected (which is why I figure a 10 pulse signal is used on later cars). also, many people have used E36 OBDII DMEs with an E30 VSS signal.

And even though the input says "right rear ABS signal" what it really means, on the E46 anyway, is that the right-rear ABS signal is input into the ABS computer, processed, and then output to the DME/cluster as a 10-pulse square wave.

you could build a circuit that takes the E30's 48-pulse sine wave out of the ABS sensor and output a 5v square wave. I'm just not sure why you'd need to, or why BMW would use a 48 pulse ABS sensor signal on only one model..

[alndks]

Can i have a correct speed signal from the e30 cluster (9 pulse)?
I have to do a conversion?
Now i give signal to dme from the c101 pin 14 Black/White to brown/red and i get very very low speed from dme

[nando]

there's a way to adjust the # of pulses for the VSS output by changing a resistor on the speedometer PCB. look up the datasheet for the UAF 2115 chip. I don't know if 48 is possible but you might be able to get it closer.

if you have anything else reading off the VSS input, like the cruise control or 13 button OBC, they'll be screwed up though.

[alndks]

This will effect the speedometer (obc, cruise control)?
And when i will look?
I searching over the forums for two weeks and i cannot find the solution

[nando]

This will effect the speedometer (obc, cruise control)?
And when i will look?
I searching over the forums for two weeks and i cannot find the solution

it shouldn't affect the speedometer, there are actually 3 outputs from the UAF chip - speedo stepper motor, odo stepper motor, and square wave VSS out (the "A" line out of the speedo).

I think. You should be able to find the answer if you study the datasheet.

[alndks]

sorry if this i stupid question where i get the datasheet?
Also is any possibility my instrument cluster is faulty and not give correct signal?

[nando]

do a google search for UAF 2115 datasheet, it's in PDF form. it's a very common chip used in millions of cars so it's everywhere.

there is that possibility. you could open it up and inspect for damaged solder traces. but the speedometer works normally correct?

[alndks]

The speedometer, obc and cruise control works normally.

[alndks]

If i will buy this:

http://www.kempower.be/Electronic%20devices/BMW%20M%20speed%20simulation.htm

Will correct the speed signal?

[luckysnafu]

I noticed the same thing on my m52 when hooked up via BT to torque. Speed reading is way too low from ECU. There is an OBD Speed multiplier available in the Torque Vehicle Editor which you may want to mess around with to get the speed to read accurately.

If somebody can post the # of pulses for the e30 (48 was mentioned, anybody confirm this?) and the e36 (9 pulses from what I gather in this thread), we can get a ratio and put that in the speed multiplier in Torque and get the correct speed.

If we use 48 pulses for e30 and 9 for the e36 we would enter a ratio of 5.33333 into the speed multiplier in torque.

I'll give this a shot on my way home after work and see if it works.

[alndks]

The e30 diff has 9 pulses
The e36 diff has 9 pulses
The e30 abs sensor has 48 pulses
The e36 abs sensor has 48 pulses
The problem is that the m52 dme reads from e36 abs sensor and not from the cluster.
The cluster get 9 pulses from diff
The abs sensor has 48 pulses
48/9=5.3333
The dme reads 19km/h when i go 102km/h
19*5.333=101.327
I must get a speed signal 5.333 times up

[328ijunkie]

^Unless they do something different in the Euro Cars, the M52 ECU gets its signal from the E36 cluster just like the E30 does... Throw another speedo in there. Ive seen this happen before on a customer car. Speedo was just outputing a shit VSS signal.