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DSM CAS, pull ups and MS3Pro

t8fanning

t8fanning

8v are still cool, right?
Joined
Oct 10, 2010
Location
Vancouver, WA
The MS3Pro manual says the following in regards to crank and cam sensors:

If the output voltage stays at zero the whole time, you'll need a pull up resistor... If it is at zero volts in one stat and bounces up to at least 5 volts in the other state, it doesn't need a pull up resistor.

I just tested a spare DSM CAS. The cam position output varied from 0 to 5V, but the crank position output stayed at 0 the whole time. Why would it not vary between 0 and 5V without a pull up for both outputs? Is this a function of the sensor, or my poor measurements/or high resolution of the crank trigger? With microsquirt, I used pull ups on both crank and cam signal and it worked. Should I do the same with MS3, despite the cam output not necessarily needing it?
 
So the CAS is powered up with 12 volts and you are getting a 0-5v signal on the cam sensor output with nothing other than the voltmeter connected to the output? That is unusual. The 'typical' CAS arrangement requires pull-ups on both sensor outputs. Perhaps it is something unique to the original application that the CAS came out of. What car was the CAS originally intended for?
 
It's powered with 12V and I see a cam signal varying between 0 and 5V between the cam output and ground while I rotate the shaft.

No idea where this CAS came from, but it is the older style with the plug not on the body.

Either way, I'll put pull ups in my new harness.
 
Broke4speed said:
I could NEVER get the DSM CAS to work with my MS3Pro. I tried every combination of pullups on every combination of wires, but it just wouldn't give me a tach signal.
Click to expand...

Are you sure your sensor was good? It was easy to set up with microsquirt, so I'd imagine it's not much different if at all for MS3Pro.
 
t8fanning said:
Thanks for the definitive answer. Any tips for best practice installing them? Just some crimp sleeves and support it with heat shrink so the legs can't break?
Click to expand...

That works. My own personal preference is the thick heat shrink with the epoxy liner to ensure the resistor doesn't move around in the wires. The thin stuff doesn't support it well enough, seen plenty of failures with the legs breaking off at the body of the resistor as a result.
 
the included pull ups for optical/hall sensors have worked like a champion on both of the ms3pro's I've installed on volvos.
 
For Ms3x you need a pull-up on the crank sensor. On the cam input you can adjust it by turning the pots in the Ms3x manual to get it to work. I would imagine Ms3x pro would be the same way? I don't know for certain though
 
t8fanning said:
Are you sure your sensor was good? It was easy to set up with microsquirt, so I'd imagine it's not much different if at all for MS3Pro.
Click to expand...

I have 4-5 of them here (also a DSM masochist, lol), and they all gave the same result.

I'm sure I was just missing something, but I gave up and went external crank wheel. It's much easier to just pretend I never tried, than to admit I was too stupid to figure it out after nearly two decades of standalone installs, lol.
 
shaved240 said:
I would imagine Ms3x pro would be the same way? I don't know for certain though
Click to expand...

On MS3X you have to jumper the pull-up on the expansion board.

MS3pro is entirely different and does not have this. Pull-ups must be used, as mentioned before.
 
No, it was on a VW project I was working on. Years back I made an adapter to run a DSM CAS on a VW DOHC engine, and used a DSM harness/management too. It ran great, but then it got parted out due to boredom. I kept the adapter and wanted to try again on a different project, but same engine. I went with MS3Pro this time, and just couldn't get a tach signal out of it :(.
 
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