Audiovx APS 685 wont program

I have installed an audiovox APS-685 remote start in a 99 nissan altima. I cannot get the unit to go into programing mode to set the tach signal

one thing i have learned is that an audiovox has two switches one to turn the remote start on and off ond the other plugs in to a blue port it is for programing.

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zargon ruler of estranorth

If it won't learn tach, you might not have the right tach wire.  Where did you get tach, and what color?  If I remember right, I get WHITE/ blue, at the ECM under the center of the dash.

To program audiovox systems to read the tach you have to flip the valet switch (grey and black wires w/o red cover over switch) 3 times (off, on, off, on, off, on) with key set to ign. position. You should here the module click (if not then repeat or test your power and ground wires) then turn key off turn valet to off (parking lights will blink if learned, or flash 7 or 8 times to let you know tach wire is not correct. Once lights flash flip valet switch back on (pkg lights stay solid) - Tach is learned

sometimes the audiovox units are picky. try remote starting the unit first without programing tach rate, the unit should flash the parking lights 7 times to indicate that the tach has not been programed. turn the ignition on, push the black pushbutton switch 3 times, turn ignition off, HOLD down the switch while you start the car and the parking lights should start flashing to indicate that tach has been learned. if this doesnt work, first double check where you got your tach signal as someone has already posted, then if all else fails, check that the switch is actually working, take your probe and make sure one end of the wire is going to ground when you push the button, it could be something as easy as a broken switch... not likely, but it is possible.