Swapped OBDII VSS fault p0500. Electrical gurus needed

[benz-tech]

I am running into one last issue with my odb2 m44 swap into my late 318i. And before the flames come, I did this to essentially get more power, reliability and economy than my tired engine could offer with an easy work around come smog time. The lure of knock sensors, and a MAF eventually moved me to turn it into a running obd2, ews2 40 mile per day driver w/ DME 5.2

Now the issue: I am plagued with a p0500 code a5,500 rev limit, and no live speed data from the obd2 port. Pin 14 is hooked up to pin83 on dme for 'vss input'. A scope shows this to be a 5v signal with downward spikes, but not a pure square wave. The pattern gets a little dirty when hooked to the dme. I've tried getting signal from pin 14 and then from the back of the obc (br/rt). Hell I ran a wire straight from the diff sensor. Nothing I've tried works. Of note is that pin 83 has 12v on it when disconnected from the vss output.
The swap is from a 96 318ti manual w/o traction control.

Does the e36 ABS module send the vss (or even a backup signal) to the DME VIA the data link? Any experience with the VSS needing to be a 12v signal. Should the output from the speedo be a square wave or will it spending most of its time at 5v with drop dow spikes be good enough.

The only fun part of driving a M42/44 is revving the piss out of it. Take that away and what's the point?

[Northern]

With the MS41 ECU on the M52/S52, the ABS sensor sends wheel speed to the dash, which conditions it and sends it to the ECU. In the e30, it originates at the diff, which makes a signal 5.33 times too low (48 teeth vs 9 teeth). There is a value in the ECU that can be edited to compensate for this.

I would assume the M44 E36 would use the ABS signal also, and might suffer from the same calibration issue? The fix would be to find and correct that value in the DME, but I don't know what kind of aftermarket support there is for DME 5.2

[benz-tech]

I would be happy with a too-slow reading. Its just that I have nothing at all. Is there a discrete signal from abs to dme on the m52 type dme?

Edit:
"5.2 has no direct abs line but does have a vss input pin from the cluster"------it does when you have an accurate wiring diagram. There are supposed to be 2 speed inputs! It's nice to know that NOW.

[benz-tech]

A different wiring diagram shows a rear wheel speed sensor signal from the abs module at pin 79 where as the diagram I have says 'not used'. I hope this solves the problem. I will have to work out the right type of signal to it. 5.3 times faster than the vss from the cluster.

[328ijunkie]

VSS on E30s is a filtered signal directly from a pin on speedo. If youre not getting a signal at all from speedo, i see them go bad from time to time and cause this issue.

[Axxe]

If you don't care about having accurate vehicle speed at the ECU, we just fed the VSS line the tach signal to get a non-zero value. Boom problem solved (we run GPS datalog for road speed).

[benz-tech]

Yeah problem solved. I fed the speedo output to both pins on the DME and voila, full rev range and a very slow vss speed on the data steam. Good enough for me, as long as its not used in calculating fuel and timing maps. Got dam incorrect 20 year old wiring diagrams!

[328ijunkie]

I'm not super well versed in M5.2 but ms41 uses it in a few places for somewhat important stuff (vanos). Most tuners correct for the lack of it though(or they should)

[Andrew325is]

I just found this thread. So here's some info just in case it helps anyone else experiencing this issue. The description for pin 83 on the M44 DME in the ETM is wrong. That's not vehicle speed. It's the fuel consumption signal output for the cluster. That's X20 pin 24, so same as on a 6 cylinder. The vehicle speed signal is X20 pin 9 (from ABS/ASC module), which is pin 79 on the DME, so that's why the issue was solved after hooking that up. Mine still trips a code for vehicle speed signal, but no issues revving. It hasn't tripped the check engine light, but it shows up on the code reader as pending.