soot

So I'm not a huge electrical wizard and I'm running into some trouble. I have a MS3 Basic from rev and I was previously running Toyota cops and my tach worked fine (tach signal come from coils, so we're good). I just swapped to a VVT engine and I need the MS to send signal to the tach, but I'm getting nothing.

Tach out is set in tunerstudio and I was getting nothing connecting my tach out wire directly to the cluster. I hooked a DMM up to the tach out wire and I'm getting ~8v at the wire instead of 12 (I assume I should be getting 12 in that wire based on what I've read on forums). Does anyone have any thoughts on what might have failed? Seems like there's a HW issue in the ECU I may have fried at some point?

der_vierte

I'm in the same boat (ms3 mini)

LocoRocoNL

Following, running Toyota COPs on MS3 Basic for my VVT NA6.

soot

If you wire your cops in per this thread your tach will work. I was previously running previously without any issues.

My issue is with no tach on coils that have no tach out where you need a signal from the ECU

Reverant advised tach out should have "12v with the ignition on, engine off. 6-9V with the engine running as the tach signal is 50% duty, so about half the running voltage." I'm probably missing something dumb. I'll poke around more tonight and post back after.

MX5RACER

Double check your MS has the Tachout circuit, you will also have to add a 1k resistor in the diagnostic box. I was getting a weak tach signal with my coils that would cause the tach to bounce a drop a bit. I enabled the tachout circuit and added the resistor and now my MS feeds to the tach.

soot

Ok, further updates -

I'm getting 6V on tach out key on engine not running, and 8.5V engine running.

I depinned 2I from the ECU connector and connected tach out to that pin and still - no tach. I tried running tach out straight to 1H in the cluster and that also nets nothing.
I also tried both of these connections after setting nitrous 2 as my tach out and those also net me no tach.
All of these variations have been attempted with the 1K resistor in the diagnostic box as well.

I verified I'm using the correct tach out wire both by the pin number on the DB37, and with a DMM and tunerstudio in test mode on that output.

Here are my megasquirt settings. Any help is greatly appreciated! I'm at a total loss.

der_vierte

I've gone through all of that, too and still no tach. Till now I gave up and hope that someone is coming up with a fix some day

natewin

Interesting. When I wasn't running tachout and using 95 coils I had the resistor. When I switched to Tachout and LS coils I do not need a resistor. In my case I would recommend one or the other, not both. I don't think having Tachout enabled and a wire or wire+ resistor from coils is a good idea. I don't know enough to know if this could damage something.

Reverant

iTrader: (10)

Do not follow any stray guides for MS3x or anything else. Just connect the tacho output from the ECU directly to the yellow/blue wire which can be found on:

1) The igniter wiring (disconnect the igniter!)
2) The diagnostic port in the engine bay
3) The cluster wiring

Do not connect the tach out output to IG+ or ANY other wire, or the output may be damaged.

natewin

Thanks for confirming Rev. I didn't think having both sources would be a good idea.

soot

Hi Reverant! Thanks for responding to my DM. Just to clarify for the folks here - I have only ever attempted to connect tach out (pin 10 on my MS3 Basic) to 1H (tach in cluster) or 2I (tach output from ECU that leads to ignitor wires that are connected per the VVT Megathread with the igniter removed - pin 4 yellow/blue to 5 black/white.)


I did buy my ECU used and I suspect that the tach output may have been damaged at some point as the tach should work with my tunerstudio settings and wires 4 and 5 connected to each other. Even if that didn't work it should still work when the tach out is connected directly at the cluster, right?

soot

Rev helped me sort things out! Just for closure on this thread

• I have an older MS3 Basic
• I connected pin 4 and 5 where the ignitor used to be (pic in my last post)
• VVT coils
• Tach out was not working with setting enabled in ECU - tach out was apparently damaged (due to me or the P.O)

I am not currently using pin 19 (nitrous 2 out) on the DB37 so I decided to make that the new tach out using Rev's instructions

• Soldered a 2.2K resistor between pin 1 (12v) and pin 19 (nitrous 2 out) inside of the ECU case
• Set tunerstudio to output tach on nitrous 2
• If you have previously added a resistor in the diagnostics box between ig- and b+, remove it
• Depinned 2I on ECU connector and then wired it to pin 19 on DB37 (tach wires are still connected at ignitor)
• Working tach, happy me

If you're a noob like me, using a DMM to check that I was using the right pins the whole time made this a lot easier.

natewin

Nice. Thanks for closing it out too!

LocoRocoNL

Adding on this as it was not clear for me. Pin 2I on the normal ECU connector is connected to nowhere. Meaning that you have to connect the wire on 2I to Pin 10 on the DB-37 connector in order to have it working at all.

Copy paste from what Rev sent me: