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1G green wire for tach install??

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ShakeyTalon

Probationary Member
7
0
Feb 14, 2005
Macon, Georgia
ok, i bought this car as it sits, its a 90 tsi awd w/ a jdm 4g63t swap(from what yr model i have no idea, our best guess is its from a galant), i know the gauge cluster has been switched out, but from what yr model i dont know....the factory tach doesnt work, which im ditching anyway for an autometer unit, ive seen where on a 90 you are supposed to tap into the ecu, but on later models its ok to tap into the tach wire under the hood.....my question is....which do i do? i assume it still has the usdm ecu in it....so do i go for the ecu or under the hood......if i should go to ecu, which/what connector do i go to, ive had one hell of a time finding this info local or on vfaq (im search impaired, i can never seem to hunt down what im looking for)

thanks in advance for any help
shakey
 
anyone w/ any input?
 
im getting mixed info from everywhere....all of the following info pertains to installing an aftermarket tach in a 1g by tapping into the wires at the ecu

1.according to apexi i would need to use the pin in the middle connector, (#54) Power transistor for #1 and #4 coils (which would only read 2 cyls right?)

2.according to a vfaq safc install for vr4's and 1g's i need to use a pin on the 24pin connector (#16)16 Barometric pressure sensor (MAF)

my idea after searching for the last couple days is to use the pin #21 on the 24 pin connector for Crank angle sensor (RPM), since it is the only one that mentions anything of rpms in the entire pinout

i know theres somebody out there that has installed an aftermarket tach in a 1g, any help is appreciated


for my pinout reference click here....
VFAQ 1G pinout

again, thanks for any help
 
from that model you linked to i'd say it's pin 21. IF i remember correctly there was only 1 pinout for RPM [ but that's for a 2g ] .

why dont you just seperate a little of the wire and do a temp-tap and see if it works?
 
Hi guys! I want to install an aftermarket tach on a 1990 ecu. I tried pin 109, 21, but they don't seem to work and pin 58 just pulses 200 rpm on the gauge.
What i dont understand is that ecmlink perfectly reading rpm.
 
No no no. Pull the dash cluster out, add a wire to the "tach" screw and go on about a day of "dam, why didn't I know that". :ohdamn:
Marty :sneaky: :thumb:
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If this DOESN'T work, let me know but I'm 99.9% on this since I tap it for shift lights and RPM readings for an after market TCU.
 
No no no. Pull the dash cluster out, add a wire to the "tach" screw and go on about a day of "dam, why didn't I know that". :ohdamn:
Marty :sneaky: :thumb:
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If this DOESN'T work, let me know but I'm 99.9% on this since I tap it for shift lights and RPM readings for an after market TCU.

Sorry, it's not a dsm. So i don't have the stock gauge cluster. My aftermarket gauge has 3 wires red black green.
And has some settings for 1 to 12 cylinder. I wired the whole car but something easy as this, i can't figure out!!!
 
It's right there in the factory harness that supplies the dash. I am at work so I can't run it down on a schematic but the tach signal is on one of the wires that used to plug into the dash, if you still have those. Good luck, trying to help is all.
Set the tach to 4. The red is 12v, black is ground and green is tach feed for your new tach btw.
 
Thanks for the help man i really appreciate it.
I'm driving the car with 1990 ecu and 1993 wiring harness and sensors. That's all im using from the dsm wiring. Is there another way to get the signal from the ecu ?
 
Is the dash connector still there where we can grab the signal from, the one that plugs into the back of the stock dash?
I have a 92 Factory Service Manual, but I am at work. It would show which wire on that harness is the tach signal. I might be able to help later, when I can open it up and see if I can find it.
I can see it is the 3rd wire from the end, but can't tell which end. It can only be 1 of 4 wires that are the 3rd from the end of the connector so there you have a 25% chance on the first try.
 
Is the dash connector still there where we can grab the signal from, the one that plugs into the back of the stock dash?
I have a 92 Factory Service Manual, but I am at work. It would show which wire on that harness is the tach signal. I might be able to help later, when I can open it up and see if I can find it.
I can see it is the 3rd wire from the end, but can't tell which end. It can only be 1 of 4 wires that are the 3rd from the end of the connector so there you have a 25% chance on the first try.

No sir i only have the 1993 engine wiring harness and 1990 ecu. I don't have the interior wiring harness. Just want to know which wire at the ecu i can use for the tach signal. Because ecmlink is reading the rpm perfectly fine.
Thank you again
 
1990 ECU...., I can grab my FSM for that and find the wire for you. I will be a good hour before I get home so bear with me. :)
So are you plugging the 93 harness into a 90 ECU, just so I have it straight?
 
I have installed some digital and analog aftermarket tachs on my 90 DSM. some take the signal from pin 21 or pin 54. Also some take it from a injector signal pin 51.
If I remember correctly, for an analog tach I took the RPM signal from a thick white braided wire which goes to the stock cluster I guess. And adjust the cylinder number. For instance, if the idle is set at 800rpm and you read only 400rpm with the number of cylinders "4" then you select the number of cylinders twice more 8 cylinders.
 
Well ECMLinks wiki shows pin 109 for the tach...
I don't know about the 90 as I can't find its pinout in my FSM but I'm still looking.
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Here is the 1990's way of sending the signal to the tach, per the FSM.
The tach filter splits the signal and the raw form goes to the ECU pin 109, the other split goes thru the filter then to the tach. I have about a dozen articles you could reference. I am trying to put them all on one WORD document as links for information.

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I have installed some digital and analog aftermarket tachs on my 90 DSM. some take the signal from pin 21 or pin 54. Also some take it from a injector signal pin 51.
If I remember correctly, for an analog tach I took the RPM signal from a thick white braided wire which goes to the stock cluster I guess. And adjust the cylinder number. For instance, if the idle is set at 800rpm and you read only 400rpm with the number of cylinders "4" then you select the number of cylinders twice more 8 cylinders.

Ok thanks for the input. I'll give it a shot this weekend

Well ECMLinks wiki shows pin 109 for the tach...
I don't know about the 90 as I can't find its pinout in my FSM but I'm still looking.
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Yes i tried pin 109 a few times with no luck.

1990 ECU...., I can grab my FSM for that and find the wire for you. I will be a good hour before I get home so bear with me. :)
So are you plugging the 93 harness into a 90 ECU, just so I have it straight?

Yes, i believe i only swapped pin 6 and 14. And it fired right up!
 
Do you have a 90 tach filter installed also? That is key.
 
Glad you reported back so others can use the information and glad you got your aftermarket Tach to work, that helps us all.
 
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