Another Tach Question. (Did search first!)

[trunknuts]

2005 5.3L (Tahoe motor) in a 93 Silverado. Got almost everything working so far. What I'm having trouble with is the Tach signal. I'm using an Auto Meter tach. I tapped into Pin 10 (white wire) on the green connector on the PCM. I also set the tach to 4 cylinder (2 pulse I believe). With the tach plugged in it moves ever so slightly when it first gets power. When I connect the "signal" wire to the white wire on the PCM nothing happens. The tach doesn't work. If I take the "signal" wire on the tach and repeatedly tap it to a 12V power source (simulating an AC signal) the needle does move around, up to 7k RPM. I've checked the ground and power sources with a digital multimeter. They seem fine. Does anyone know if the white wire on pin 10 still have the RPM output? Was there a change in '05 or earlier? I'm so frustrated with this. Any help will be greatly appreciated. Thanks again!

[NITROUS]

You need to change the tach resolution in the PCM from 6 to 3 or get a module from Dakota Digital to convert the signal. Who did your tune? Send it back to them and have the resolutiuon changed if you want to make things easy.

[trunknuts]

Thanks again NITROUS. I'll check out Dakota Digital. Wait4me Performance did the tune. I'll also contact them tomorrow and see what they say.

BTW... is this what I need?
Dakota Digital - digital instrumentation and accessories automotive and motorcycle enthusiasts.

[Chevy-Art]

I'll be doing this soon too, thanks for the info.

[RedHeartbeat]

That or you can contact BakerElectronix.com and get one of his adjustable resolution tach modules.

[trunknuts]

RedHeartbeat... is this the adapter you are referring to?
http://mysite.verizon.net/vze7erz1/s...files/atsd.pdf

Also, If I understand this correctly I need to convert the 4 cylinder signal to an 8 cylinder signal? Shouldn't the aftermarket tach be able to do this with the dip switches? I'm not arguing I'm just trying to make sense of this. Thanks again.

[RedHeartbeat]

You can use that to change the signal count to your tach module if you don't have a PCM program to modify it.

[NITROUS]

Ya, I forgot about Baker Electronics........They will probably save a little money over Dakota but the cheapest way is the resolution change with HPTuners or EFI Live.

[beater6.0]

i have a problem with my 98 and i have module could the tune cause it not to work i have tried a diffrent tach. and i do have the baker module.

[trunknuts]

i just spoke to a tech rep at auto meter. He says that the RPM output of the PCM on the LSX based engines is carried on a 5V square wave signal. The Auto Meter tach required a 12V square wave signal. Autom Meter offered to changed the input requirement on the tach at no charge if I send it out to them. But who knows how long that would take. They also mentioned that they have an adapter for that exact application. Auto Meter part number 9117 Tach Adapter. "This adapter senses the current from the positive coil source wire and converts it into a 12-volt square wave signal that can be read by Auto Meter Tachs and accessorie."