jawatkins95

Hello,

I'm running a Haltech Elite 1000 with the PNP harness for my Mazdaspeed Miata.

I've been messing around with launch control and the likes and noticed that the ECU is not getting a vehicle speed sensor from the current wiring arrangement. The PNP harness has an input dedicated to VSS but it's not picking up a signal regardless of how I configure the settings.
Has anyone else run into this problem?

Items of note:
My car is running a 5 speed instead of the factory 6 speed. My understanding is that the factory speed sensor signal originates from a sensor in the trans. This may be an issue.
I previously had a Hydra 2.6 installed in the car with the PNP harness; that ECU was getting a VSS signal as it would log speed in my datalogs.

The next step is to put the car on jackstands in the garage and start probing with a multimeter, but that kinda sounds like a pain.

msmola2002

Check your i/o

the base map had VSS on SPI1 and the harness was SPI2 or vice versa. Double check the specified input is correct on the map vs what is specified in the QSG

nuggys.nb

Did you ever get to the bottom of this?
I have the same issue.
On the VSS pin (3T if I remember right) the signal is all over the place.
I've tried pulling it up to 5v, pulling it down to gnd with 3k resistors, even had a scope on it.
Scope shows lots of noise which seems to be linked to ignition events, and some pulses do come through when starting to roll but they barely peak above the noise.

Maybe my issue is different, just wondered what your progress was

jawatkins95

So I'm just now getting around to troubleshooting this.
I haven't made any progress in the car yet but after looking at the wiring diagrams it would appear that the signal ground for the VSS is on pin 3O on the ECU harness. Did you have the scope referencing chassis ground when you were making your measurements or did you just leave it hanging? That could explain some of the noise; really you would need a grounded probe connected to 3O on the harness to check properly.

My plan is to check continuity on the PNP adapter and verify that pin 3T from the stock harness is in fact connected to pin 9 on the other side of the adapter. Then obviously make sure that the wire from the adapter to the ECU is pinned to the right spot.
I also want to verify that 3O is connected to the signal ground circuit on the Haltech; if not that might explain the problem.

jawatkins95

Update: After removing and re-installing the transmission as part of the engine block venting repair process, I magically detected a working VSS signal on SPI2 as expected with the pnp harness. I assume that something was not plugged in properly.

​​​​​​Sensor input is configured as a hall effect with a pull-up. Appears to be generating a nice, clean square wave for me.