LT1-LT4 Modifications - LT1 tach output issue, tach reads double actual

OBDII PCM, is there any "tach output pulses" table that would change the tach signal to the dash?

I have a caprice that shows double on the dash then what it looks like actual/in the datalogger

Is this the stock Caprice gauge cluster?

yes, aftermarket tach reads same

Well if it was an aftermarket tach I would say you have the wrong wire cut or uncut.... But since the stock tach is reading double you got me...

by any chance is there a ls1 in the car your speaking of? if so then that explains it

and to answer your question yes it can be changed in the tune...

or check the pcm and see if its an ls1 pcm or the so called 411 pcm retro fitted, that would throw it off also....

some place sells a box that converts the tack signal to work with the lt1 gauges if you have an ls1 pcm..

or check the pcm and see if its an ls1 pcm or the so called 411 pcm retro fitted, that would throw it off also....

some place sells a box that converts the tack signal to work with the lt1 gauges if you have an ls1 pcm..

I just ran into this with my 2002 corvette LS1 conversion going to my stock tach in my 1997 camaro. The problem with LS1 PCM is that it outputs a 4cylinder pulse. My LT1 tach was looking for a 8 cylinder pulse. I used a dakota digital tach module, (SGI-8) and tapped into the white wire on my C230 cable in my kick panel)

The module lets you choose tach output and then you can also manually adjust tach with up and down arrows. Hope this helps. Based on what your saying about double speed makes me think you need to convert to half the cylinder output of whatever your pcm is putting out to your gauge.

OBTW I tried changing the pulses in HP tuners with no luck for some reason.

No, lt1 motor, bbody PCM both OBDII

I had no problems with my LS1 into my 97, change the pulse per field in HPT, changes tach on dash

I just swapped a 2000 LS1 into a 1997 WS6.

I had to change the High and Low Tach Resolution settings in the tune from the stock setting of "6" to the value of "3".


Hope this helps anyone else looking for this answer.