Tach wire

[kglowacky]

trying to measure my rpms on my truck at 60 mph. it is a 2002 ls1 with 460. My question there is one wire on my harness labeled tach from my harness builder. What signal is it putting out? Can I just connect an old school tach to it and will it work. Not looking for a long term solution just want to see what my rpms are. See if my overdrive is working.

[clay68c10]

It depends what the tuner set it to, but it should work.
So will a generic code reader. I would think you already have one of those, no need to buy anything else.

[Joyridin]

Usually they are set-up for a 4 cyl type of signal, so I think you might have to run a tach on 4 cyl mode (not 100% sure). I know on my later style computer, I can change the tach signal relatively easily by making adjustments in HPTuners.

[LeesTruk]

If you use an aftermarket tach, you can usually set them to 4, 6, or 8 cylinders. The PCM puts out a 4 cyl. signal, so set the tach to 4 cyl. or have your tuner set the PCM to 8 cylinder signal. Either way, you're gonna need to add a pull-up resistor to the white signal wire (usually 1K to 5K resistence of at least 1/2 watt), as well as boost the signal with a 12v switched source.

[LS short box]

I've always used Auto Meter tach's on my LS swaps. Yes the ECM sends the signal to the tach. On the back of the tach are dip switches that can be set for 4,6 and 8 cylinder. LS ECM's use the 4 cylinder setting.

[kglowacky]

someone told me i can buy a plug in something or another that plugs into my pcm port that will read rpms and then i can read it off my phone. ???????
LOL I lack any knowledge of new technology.

[LS short box]

Yeah you can buy some type of widget that plugs in the OBD port and blue tooths into your phone. I know they make one for the Android but not sure about Iphone. I'd check over on LS1tech.com.