My tach and the tach on my AVCR read about 50% of the actual RPM?
My Haltech RPM reads accurately?
I have swapped the trailing coil and grounded everything to death and it still does it?
Any ideas?

 

Someone just had a post where they had the same problem with the s-afc. Is it all of the sudden or is it a new install?

 

It's all of a sudden. Was working just fine.
The thing that gets me is, all the devices are reading from the same lead?

 

So all other readings are accurate as far as you know? Damn that is strange, the avc-r gets the tach reading from where exactly since you have a haltech I believe?

 

It gets it off the trailing coil.
I'm wondering if there is some kind of resistor or something that has gone bad?

 

Well something had to change somewhere for the signal to change. I would guess it would some sort of fuse/resistor problem. I mean your car runs the same though? A ground hasn't fallen off or broke? More than likely its something simple that you're just not seeing. Those are the most difficult ones to fix sometimes