Trying to work out the kinks in my engine swap, and having issues with the tach. I've read numerous posts about different pull up resistors, and wether to use 5v or 12v circuits. The gauge company ( intellitronix) reccomended a 10k ohm to 5v. Didn't work. Played around with different resistors and found it will work with a 2k ohm hooked to 5v, or 10k to 12v. Which is less load on the circuit/less likely to damage the pcm? I know some have run as low as 680ohm on 12v, but want to play it as safe as possible.

 

If the 10K works on the 12v I would use that setup. Your talking micro amps on the pcm tach output. This will not harm anything.