Tach Signal 1UZFE Where does it come from?

[lexus082]

Where does the tach signal come from? My tachometer is registering the tach signal properly. When I first start the car its at 750 rpms and when it idles in park its between 250-500 rpms?

 

[gloverman]

From the EXT terminal on one of the ignitors - one ignitor will have 4 wires and the other one will have five - the fifth wire is the tacho - cheers

 

[200sx-v8]

I remember i got a very fluctating signal from that output. When I took it from my standalone ecu it was just fine. Never quite understood why.

 

[sideshow]

same ignitor wire goes to the ig- wire in the diagnostic plug

this wire also runs to under the dash on left hand kick panel

just trace t with multimeter

but the signal is weak and it is also a 4cyl signal so set yr tacho to 4cyl 2 pulse

some tachos might need a tach booster if they flicker or stuff

 

[lexus082]

So is the igniter what measures the rpm's? Or does the signal just get sent to the igniter from something else?

 

[sideshow]

the ignitoer triggers the coil so it will spark

there are 2 ignitors and thy do each coils

so as one ignitor fires it also sends a much weaker signal to the tacho

both ignitors can send a tacho signal but only one ignitor plug has the wire for tacho

what car and what dash are you running

is it a factory car with factory 1uz or is it

a hilux or similar with a diesel tacho

diesel tahcos need many more pulses to et to read accurate

if the tacho is not for a 1uz then u have to send it to get modified
to suit a 1uz

 

[lexus082]

I have a 94 Sc400 and the tachometer on the guage cluster isn't receiving the correct tach signal. So basically when I'm at idle (700 rpms) my tach on the guage cluster says in between 250-500 rpms. So I'm trying to trace it to where the problem is coming from. Thats why I am trying to figure out where the tach signal is created and where it is sent from. So is it both igniters that each produce their own tach signal that goes to the guage cluster's tach. needle

Or do I just need to trace that one wire that comes off that one igniter that sends out the tachometer signal? I'm not getting any error codes related to a improper tach signal. So it may be the tach needle itself mechanically failing.

 

[sideshow]

if the taho is actually doin somehting then im thinking wiring and signal is ok

but the tacho mght be on its way

 

[lexus082]

So you think its the tachometer itself in the guage cluster messing up? And you don't think the tach signal comes from the ignition coils?

 

[lexus082]

Everyone who has responded is correct. Its the Igniter #1 that sends the tach signal to the cluster. Someone gave me a diagram. Alright, well if the tach signal is correct coming off the (DLC) under the hood and my tach is displaying something else. Does it sound like the rpm gauge in the cluster is malfunctioning?

 

[lexus082]

I swapped clusters today and I found the tachometer in the speedo cluster is bad and displaying the wrong rpm's. I still have a misfire though... arrgg.