Thread: tapping tachometer wire?

Tachometer- white/green (ECM)


NISSAN, MAXIMA, 1995, Tachometer

The ECM is located in the front of the center console on the transmission hump. The wiring is easily reached by removing the small black panel just to the front of the center console on the passenger side. the wire is in the middle row, 7th one in from the left.

I dont know if you'll get much out of it.. the tach wire is just a wire that sends pulses of DC current to the injectors.. i'm not sure if it changes when it goes through the firewall and connects to the ecm.. just my 2 cents.

why not try making your own tacho pick-up, need a sender on the engine and receiver to count the pulse.
http://www.niksula.cs.hut.fi/~mdobru...cho/tacho.html

Here you go. Let me know if you need any other help.

Originally Posted by DrStein99

Does anyone know where to find the wire assignments for the harness in the dash-board / steering column? I know there has to be a website, or chart somewhere, I dont have any luck finding it.

I have a 1995 Nissan Maxima, trying to find the tachometer lead - it should be a wire that delivers a +12v pulse, each engine rev.

I'm trying to build some neat gadgets using pic/eProm software, that gathers info from the car; and I want to capture the RPM's - if possible.

Please advise.

I'm doing something similar for my own front end. I'm going to tap off the rpm/tach and indicators, read them with a PIC16877a and send them serially to the pc.

If at all possible, try and hit ebay for the service manuals for your car. I've found them to be invaluable.

Originally Posted by fixerofallthing

Negative (-) side of the ignition coil.

I think you'll have problems with reading it from there with a PIC or other mcu. It's very noisy, electrically.

Originally Posted by snova031

Tachometer- white/green (ECM)


NISSAN, MAXIMA, 1995, Tachometer

The ECM is located in the front of the center console on the transmission hump. The wiring is easily reached by removing the small black panel just to the front of the center console on the passenger side. the wire is in the middle row, 7th one in from the left.

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There are about 3 black panels, all the center of my maxima, and I dont recall any on the passenger side.

Am I looking in the hump (floor) or the one facing forward - the dashboard?

Originally Posted by shotgunefx

I think you'll have problems with reading it from there with a PIC or other mcu. It's very noisy, electrically.

You are right. That particular car is coil on plug though, so there are 6 coils. So my first response was incorrect. I posted a pic of the wiring diagram for that vehicle and the wire mentioned above is correct. It will be a very "clean" signal because it is produced by a control module for the express purpose of running the tachometer.