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Old 06-12-2009, 10:47 PM   #1
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Default Question about Location of 1999 ECU Grounds/Grounding Point

Ive tried to google, search, and look for pictures on the exact mounting point of the ground for the ECU on the 1999+ cars.

I did search and find grounding points for 1994-1997 cars though, and I know its supposed to be on the bottom right below the TB.

Is it above on the 1999 cars? I have some pictures of the wires that I THINK is the correct one, but I need some verification before I get around to fixing up the grounds of my MSI and a new LC-1 I have.

NOTE: I THINK, it might be the injector grounds now that I look at the color code, but where would the ECU ground point be?

Thanks in advance!




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Old 06-12-2009, 11:03 PM   #2
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There are no more ground points...you have circled the one PCM ground point that are actually two separate sets of wires on the 1999-2000 cars.

The injectors are grounded by the PCM internally, there is no external "injector ground" in any Mazda.
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Old 06-12-2009, 11:09 PM   #3
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Quote:
Originally Posted by mrtonyg View Post
There are no more ground points...you have circled the one PCM ground point that are actually two separate sets of wires on the 1999-2000 cars.

The injectors are grounded by the PCM internally, there is no external "injector ground" in any Mazda.
Thanks for the quick reply.

Cool, gotcha on the wires I circled.

So should I ground it all off the stock ECU wiring harness? I have a "boomslang" harness, so it shouldn't be too much of a problem just splicing into the stock ECU ground point.
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Old 06-12-2009, 11:17 PM   #4
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Originally Posted by badboy88000 View Post
Thanks for the quick reply.

Cool, gotcha on the wires I circled.

So should I ground it all off the stock ECU wiring harness? I have a "boomslang" harness, so it shouldn't be too much of a problem just splicing into the stock ECU ground point.
I am not familiar with MS, so hopefully someone can chime in on hooking up the boomslang harness.
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Old 06-14-2009, 03:48 AM   #5
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Maybe I should ask a different question.

For those who are running parallel MS1/2 on their 99' cars, where are you grounding the MS and your LC-1? are you grounding it on a specific point on the block or anywhere on the block? Or are you guys splicing into the stock OEM ECU grounds that is also on the harness?

THen again, this question would be MS related wouldn't it? Blah.
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Old 06-14-2009, 10:21 AM   #6
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Best thing is for this to be moved to the MS section.
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Old 06-14-2009, 12:13 PM   #7
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If you are running parallel, you want the MS and the WBO2 to share the same ground potential as the primary ECU, to prevent offsets in analog signals caused by ground imbalance. This means connecting them to the same physical wires as the main ECU, which on a '99 would be the black/yellow wires at 3A & 3B.

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Old 06-14-2009, 02:45 PM   #8
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Watch out for the WBO2 heater currents flowing through its ground wire. You wouldn't want them flowing through the ECU signal grounds.
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Old 06-14-2009, 08:27 PM   #9
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Originally Posted by JasonC SBB View Post
Watch out for the WBO2 heater currents flowing through its ground wire. You wouldn't want them flowing through the ECU signal grounds.
In an ideal world, he will both run a pair of heavy ground wires direct from the MS's DB37 to a point on the head / IM and connect the MS & LC1 to the stock ECUs ground wires.
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Old 06-15-2009, 08:24 PM   #10
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Great. Once I am done modifying my board for the new spark outputs (thanks Joe) and adding the inputs for the NB crank ad cam sensors for MSII (using Jason's Hex Schmitt Trigger circuits), I'm going to get around to doing it.
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Old 06-15-2009, 10:41 PM   #11
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Take note the circuit to take the NB crank/cam signals uses flip flops too (I'm just making sure you're looking at the right circuit).
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Old 06-16-2009, 01:38 AM   #12
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Flip flops? In not to electric savvy, I'm already having a tough time trying to understand some of the schematics.

This is the circuit i will be following, it was posted from you under the NB crank/cam inputs. I am leaning towards this because the simplicity and lower parts count. I also reposted Abe's circuit as well.
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Old 06-17-2009, 01:04 AM   #13
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Quote:
Originally Posted by Joe Perez View Post
In an ideal world, he will both run a pair of heavy ground wires direct from the MS's DB37 to a point on the head / IM and connect the MS & LC1 to the stock ECUs ground wires.
Heavy, meaning a minimum gauge of at least 12 for the grounds?
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Old 06-17-2009, 02:34 AM   #14
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Does the MSII accept the NB crank and cam pattern?
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Old 06-17-2009, 03:10 AM   #15
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Quote:
Originally Posted by JasonC SBB View Post
Does the MSII accept the NB crank and cam pattern?
yep, it is able to decode the odd tooth wheel and cam sensor. It is selectable under one of the trigger inputs.

MS2-Extra Miata 99-00 Input Manual
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Old 06-17-2009, 11:30 AM   #16
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Yeah. Both the scope trace and the input circuit schematic they show on the website is wrong (and I've had this conversation with 'em on the boards) but it does in fact work. There's a preset for the '99+ Miata right in the wheel decoder drop-down menu, so you don't even have to configure it manually like with the MS1 w/ NA.
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