1995 C2500 ls1 swap

[chvy=power]

I hooked the white tach wire from the new PCM to the white wire at the back of my factory gauge cluster....the tach operates now, but is no where near being accurate. At 4000rpm it's only reading around 1800rpm. I'm thinkin I may need to try the resistor trick????

[Jeebalow]

I hooked the white tach wire from the new PCM to the white wire at the back of my factory gauge cluster....the tach operates now, but is no where near being accurate. At 4000rpm it's only reading around 1800rpm. I'm thinkin I may need to try the resistor trick????

Mine did the exact same thing! It reads half of the actual RPM. If the tach moves, then everything should be wired correctly. The tune needs to be changed to a V8 signal instead of a 4 cylinder signal. Your tuner should be able to fix that easily. Of course, you can try the resistor and see if it helps before trying the tune, but I think the resistor trick was for when the gauge didn't work. Regardless it's easy enough to give it a shot first especially if you have to mail your PCM in to be tuned.

[chvy=power]

Na I have hp tuners so adjusting the tach signal won't be a problem....I'll do some research and see what it needs to be set at in the tune

[GreyChevy]

Videos man! We need more videos!