Factory Tach Pickup
 

Right now I'm trouble shooting my tachometer. It's from RW Gauges and it uses the factory tach pickup. The tach wires just plug into the line from the pickup that are in the wire harness by the fuse box. The gauge is acting fun though, it has my idling like 250, almost like the pickup is weak. I replaced the capacitor that is in the wiring diagram. (This gauge was put in like a year or to after the truck rolled off the line, so it's older... but NOT from the factory.) So I'm thinking it's maybe the pickup by the harmonic balancer, I don't know, it's almost 1 in the morning so I have the look at it after work. Also with the pyro, also from RW... it seems slow in responce. It only has the two leads from the probe going to the back of the gauge. The probe is in the downtube, I thought I saw somewhere pyros the were calibrated for before turbo and after turbo, and the whole thing is setup the way the manual says so I don't, more trouble shooting I guess. Help would be appreciated, Thanks!

if it was your crank sensor your alt. wouldn't charge the battery and the computer would think that the engine is not running.

I'm interested in this too .. as sometimes my factory tach reads normal. And other times it doubles my actual RPM speed [nonono]

Factory Tach
 

I'm having problems with mine also. I don't have any manual or book telling how to trouble shoot it. It didn't work when I bought the truck about 1 1/2 years ago but would like to get it working.

Yes! Thankyou for having the same problem hahaha! mine was fine, and I would say about anywhere between now and January it started to read higher, and yes even double what it should! Ive hit 4g! hahahah, so, what the hell is the problem?