Tach Pull-up Enable B5402

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April 30th, 2015
andrewjamesbond1

Tach Pull-up Enable B5402

Hey guys, have a 1995 S10 that I swapped with an LM4 out of a trailblazer. The tachometer in the s10 doesn't show rpm with the engine running. I have heard you have to have a "pull up wire" with a resistor to boost the signal into the tachometer. I don't have that wire put in yet.

Going thru the tune, I noticed this Tach pull-up enable feature under System->Tach->B5402.
Currently it is set to yes, and my tachometer doesn't work. Do I need to change this to "No" before I wire in the Pull Up wire ? Just curious as to what its function is, and to get my dash to read RPM's.

Let me know, thanks!y
April 30th, 2015
andrewjamesbond1

1 Attachment(s)

Attachment 18321 Attachment 18321 Attachment 18321
April 30th, 2015
GMPX

Are you sure the Tacho in the S10 is just a 0 - 12V pulse input?
April 30th, 2015
andrewjamesbond1

That I would not know for certainty. Best way to check?
April 30th, 2015
GMPX

I don't know sorry, someone who knows that car well might have figured it out.
May 6th, 2015
Jetmech442

I have the pullup resistor installed on my Autometer Tach in my cutlass. My tune has always had B5402 switched to "yes". My tach only worked properly when I added the resistor.
May 11th, 2015
Hooter

What resistor did you add Jetmech, and did you you just add it into the tacho wire on the way to the tacho???
May 11th, 2015
ProperTuningOG

Quote:

Originally Posted by Hooter

What resistor did you add Jetmech, and did you you just add it into the tacho wire on the way to the tacho???

1k ohm resistor in parallel with tach signal and ignition.
May 12th, 2015
andrewjamesbond1

I went ahead and put a pull up wire in, and the tach is now functional. This is the diagram I used.

http://lt1swap.com/pictures/tach_circuit_fix.jpg
May 12th, 2015
Hooter

Thanks guys, I will try this on a Nissan patrol LS1 swap