Those running aftermarket gauges with their swap..

[samh_08]

What is the deal with the tach signal on these engines? I have all autometer gauges, all work but the tach so far. First I need to see if the signal is even present in the wire, so how and what am I looking to see in the test?

Autometer says I need part number 9117 which means I have to cut and splice into my coil power supplies..Obviously this is my last resort. I would like to know what everyone did in order to get their tach working properly. BTW I also have EFIlive if that helps matters.

Let me know, thanks.
Sam

 

[388bu]

Is the tach working at all? Reading too high?

If its reading too high, you have to change the ECM output for the tach. In HPTuners its called Tachometer resolution High/Low. Both values must be set to 3.

I just hooked the ECM wire right up to my tach and I was done. The signal is probably a square wave im guessing and cant be easily checked without an o'scope if so.

 

[samh_08]

The needle doesnt move at all. I have good ignition and ground. I have a new tach on the way if that is the case, but I would like to eliminate all other variables. What is the reasoning for setting 'Tachometer resolution High/Low' to 3? So it divides 24 tooth reluctor wheel by 3 to make a 8 cyl signal?

I assume the tach signal is a square wave with voltages 0 and 5, so if I hook my multimeter up on the tach signal wire and start it up I should get a voltage right? Most meters wouldnt be fast enough to see 0 and 5, but should show a voltage between 0 and 5 depending on engine speed.

Am I thinking straight? What year PCM and harness are you using?

 

[388bu]

Yes, I believe you should see a 5v signal if hooked to a DMM, but I have honestly forgotten all that technical stuff.

I am not sure what formula is involved with that tach setting, I just know that my stock setting was 6 and it had to be changed to 3 make the Autometer tach read correctly.

My ECM/Harness are from an '02 2500 truck.

 

[mont]

do you have to go through the same thing if you are going with a carb set up??? jawdrop.gif

 

[samh_08]

Not if you do not run into problems, but either way, the signal is the same from carb to fuel injection