Problem RPM signal MS2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to   Members

MEGAsquirt A place to collectively sort out this megasquirt gizmo

LinkBack Thread Tools
Old 07-02-2016, 10:21 AM   #1
Thread Starter
Join Date: May 2016
Posts: 3
Total Cats: 0
Default Problem RPM signal MS2

I have received an MS2 from someone with a '92 1.6 NA MX5, which I'm trying to adapt for my '94 1.8 MX5. He gave it to me because there was a problem with it, it would get (almost) no RPM signal (apparently it would not get above 120 rpm on JimStim, no idea if it got any signal on the car). I am trying to check everything to see where the mistake might be, he used the MiataTurbo wiki page to build the MS2. So far, I have found 1 thing that looked interesting. The MS2 is a DIY unit from diyautotune, with a wiring harness to connect the DB37 on the MS2 to the ECU connector in the car. In this wiring harness is a protected pair used for the RPM signal, which includes a positive and negative lead, and shielding. On the wiki page I found this diagram:

However, the diyautotune harness uses this diagram, which shows a difference in the ground wires only:

Now my question. The negative of the CKP (or CPS or RPM signal) wires is connected on pin 1 in the DB37 connector, but it is not connected to the connector used to plug it into the cars harness. I would like to ask you if any of you know what should be done with this negative wire. Should it:
A ) not be connected at all since it is not used (which would mean the wiring is correct as it is).
B ) be connected to the same place as the other ground wires.
C ) be connected somewhere else.

I've searched just about everywhere but cannot find an answer. I'm hoping since it is your wiki that was used to construct the MS2 you might know what should be done with this wire.

Thank you for your support.
Attached Thumbnails
Problem RPM signal MS2-90-93_miata_standalone_ms.jpg   Problem RPM signal MS2-mswiring.png  
markkNL is offline   Reply With Quote
Old 07-05-2016, 03:33 PM   #2
Supporting Vendor
Matt Cramer's Avatar
Join Date: Sep 2006
Posts: 2,266
Total Cats: 51

Pins 1, 2, and 7 through 19 are all grounds and all go to the same location on the PCB.
In the factory Miata wiring, the CKP / CMP "negative" signals are part of the sensor ground.
Matt Cramer is offline   Reply With Quote
Old 07-05-2016, 03:43 PM   #3
Thread Starter
Join Date: May 2016
Posts: 3
Total Cats: 0

So you are saying, even if I do not solder the wire coming from pin 1 to the ground, it will still be connected to the sensor ground through pin 7 which is soldered, because they connect to each other on the MS2 pcb?

Hmm, well, at least that eliminates one possibility, thank you.
markkNL is offline   Reply With Quote
Old 07-05-2016, 04:30 PM   #4
Boost Czar
iTrader: (61)
Braineack's Avatar
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,872
Total Cats: 1,790

use the official DIYPNP documentation. Not random DIY MS2 documentation of the world's shittiest diagram or MS3 documentation.

This documents the assemble and difference between the connector board jumpers:
Braineack is offline   Reply With Quote
Old 07-05-2016, 04:38 PM   #5
Thread Starter
Join Date: May 2016
Posts: 3
Total Cats: 0

Ok I will, thank you. Are there no differences between USDM and EUDM first gen MX5's/Miatas (concerning the ECU)?
markkNL is offline   Reply With Quote

Related Topics
Thread Thread Starter Forum Replies Last Post
1.8 MP62 Supercharger Kit. MS1 (99-00), AEM, Link, Gauges. douginjenison Miata parts for sale/trade 7 08-17-2016 04:18 PM
Budget Build ~250hp review of parts/services/longevitiy/costs the_enginear Build Threads 238 07-16-2016 08:35 AM
did the dyno today 1993 1.6 stock+turbo pl11 DIY Turbo Discussion 9 04-17-2016 12:18 PM
DIY lightweight crank Madjak Engine Performance 20 04-12-2016 11:16 AM
Ms2 PnP Rev built Problems captain_kjr MEGAsquirt 3 04-08-2016 10:38 PM

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -4. The time now is 05:24 PM.