what wire do you tap into on the lt1 cars(97 SS' in particular) to wire in a tach wire???

thanks!

 

Hey man. I did a 'google' search for 'PCM tach Lt1' and found this thread. Read from the bottom up to make sense of it <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

subject: [ma] tach signal wire?

I believe I used pin 5 on the black connector. Check out this exchange I
had with an autometer tech...

Mark Wisniewski
97 Formula

Mark,

It appears pin 13 would be a tach out, as well. The ICM is like the "brain
box" which controls the ignition coil, and it is located on the driver's
side of the engine, in front of the valve cover, and will have a four wire
connector.
Subject: RE: shift lite installation


Ward,

I checked out a friends Service Manual Last night. I wrote down
these pins
which seemed likely candidates:

Black connector:
pin 5 ignition control

Red connector:
pin 13 tachometer feed

I'll try 5 on black as you suggest. Would you think both 5 on black or 13
on red would work?

BTW is the ICM what I would call the coil?

From: Auto Meter Products
I apologize for the misinformation. You have two options; 1) go to the
ICM(ignition control module) and find pin B, which will be a
white wire, OR
2) on the black PCM connector, which should be beneath the blue connector,
and tap into pin B5, which will be white also. Either wire
should provide a
tach output reference signal, for you to splice into for the shift-light.

Again, I apologize for the wrong info.

Ward

To: 'service@autometer.com'
Subject: RE: shift lite installation


Thanks for the reply. My blue connector only has 32 pins. I
pulled the PCM
out. Unhooked the wire harness labelled "BLUE". Opened the
plastic harness
connector to see the pin numbers. No 35 pin. I guess I need more help.

Regards,

Mark

From: Auto Meter Products [mailto:service@autometer.com]
Sent: Monday, March 13, 2000 5:47 PM
To: Wisniewski, Mark
Subject: RE: shift lite installation

Mark,
No, actually you will need to connect to pin 35 off the "blue"
connector, to
obtain your engine RPM reference signal.

Ward
Tech/Service

From: Wisniewski, Mark [mailto:Mark.Wisniewski@compaq.com]
Sent: Sunday, March 12, 2000 9:15 PM
To: 'service@autometer.com'
Subject: shift lite installation
Hello,

I have just purchased a Autometer Pro Shift Lite. I've read
that I can
connect the signal wire to a wire at the computer:

"Hook it to pin53 (solid white wire) on the 80pin Blue
connector at the
PCM."

Is this correct for my 95 Pontiac Formula with LT1?

Thanks and regards,

Mark

 

I am running a shift light and a MSD window switch for nitrous and both are running off the green wire coming off my coil.
That is the direct tach line, just get a wire tap and connect your wires, and you are in business.