Help needed finding tach signal on 1UZ

[new2mud]

I need to find a tach signal for a remote start install, and the location is supposed to be the black wire running from the ignitor.

I thought the signal was supposed to be an AC signal from 1-6V depending on RPM?

However, when I tap into the black wire at the ignitor, the AC signal just jumps all over--reads 1.6V for a bit, then up to 20 or 40V, then back, even on a smooth idle.

Am I tapping into the right wire? (This is a 1990 LS400)

 

[Zuffen]

Pick up your tach signal from the initer witht eh extra black wire.

I'm pretty sure it's the middle wire on the igniter plug.

The signal is for a 4 cylinder as you're only reading half the ignition system.

 

[new2mud]

Pick up your tach signal from the initer witht eh extra black wire.

I'm pretty sure it's the middle wire on the igniter plug.

The signal is for a 4 cylinder as you're only reading half the ignition system.

Thanks Rod.
To clarify: I found a wiring diagram:
on the "igniter with the extra wire," the middle wire is black/white stripe labeled "IGT" on the wiring diagram, but one of the wires next to it is solid black and labeled "TAC".

It's the "TAC" wire that will provide the needed signal, no?

 

[Zuffen]

Mud,

I'm pretty sure you're right.

I wont do any harm the pick up a signal and see what you get.

 

[new2mud]

Despite getting an AC signal that is supposedly not what the remote starter wants to see, as far as I can tell from wiring diagrams, etc. this is the correct wire.

We'll see if the remote start wigs out when it gets this signal.

 

[madmont]

Should not be too hard. It is the wire that goes to "IG-" in the check connector.

 

[new2mud]

I got it wired up using the TAC wire, and it starts just fine under warmer conditions. Morning should tell whether this signal is correct, when it needs a longer crank cycle at 15 degrees F.

BTW, where is this check connector--driver's side foot well or in the engine compartment?

 

[madmont]

Check connector is in engine compartment near the oil filler and has DIAGNOSIS written on it

 

[new2mud]

Thanks Mad.

Any idea what the connector by the driver's left shin is used for?

 

[new2mud]

OK--wasn't as cold this morning as I expected, but still cold enought to require a longer crank cycle.

The TAC signal was indeed correct, as the remote starter applied a longer crank to the engine--~2 seconds. Once it was warmed up, it significantly shortened the cycle to less than 1 second.

Thanks for the tips guys.

 

[Zuffen]

The connector by the drivers shin is a diagnostic port for the vehicle in general.

Just discard it.

 

[sideshow]

just run it to one of the coil trigger wires

since u dont need a proper tacho wire for rpm on a tacho

the rpm from one coil will be like a 2cyl engine so hopefully this is good enough anyway i recently fitted a remote start to a car and you have to understand what probs you can have

even though if car is auto its still a pain

make sure when u remote start it in mornin that when you eventually hiop in car you turn remote start off then start it with ign key

if you dont do this you can run into probs

hard to explain unitll you actually test it

as i had afew probs and tol cutomer that u get what u get and this is how it works so dont complain

 

[new2mud]

The black TAC wire worked just fine, and provides the perfect crank whether cold or warm engine.

I've had a remote start on every car I've owned and never once had a problem with starter grinding, overcranking, etc. Even after remote starting, I just hop in, turn the key to ON and take over from there (as soon as you hit brake it releases control back to the key anyway).

 

[sideshow]

thats a neat trick with the brakes im not sure if the kits i wired up have that option

 

[Spinall4]

I've learned that the way to test some of the tach signals I'm not sure about on the remote starts (DEI brand only, I don't work with anyother) is you can hook them up and see if the tach programs, if it does your usualy ok with the dei units. Do not be worried about low voltage (.5 volts ect) as long as its ac, & increases with RPM you should be fine. these are designed to work off of 1 fuel injector or 1 single coil from a coil on plug ignition.

I have my viper 791 wired to one of the wires at the ignitor (can't remember color off hand, pretty sure it was what directechs called for for 97 SC400). It starts fine even on the coldest of mornings in utah (0 degrees f).

 

[new2mud]

Yup--the TAC wire was indeed correct--although it didn't register the voltage range that the DEI install manual wanted, the "tach learn" feature on the DEI learned the signal immediately.

It has worked perfectly for 0 degree morning longer crank cycles, to very short crank cycles on a warm engine.


Good tip in the future to just hook it up and try the tach learn on the DEI units.

 

[new2mud]

thats a neat trick with the brakes im not sure if the kits i wired up have that option

I can't think of any units these days that don't have this feature--should be pretty universal to hand over "control" to the key in the "on" position once you hit the brake, hence ending the remote start timed algorithm.