Factory Tach Usage/INOP - LS1 Transplant
 

Originally a TPI 5.0 Liter, I've completed the transplant with a 2000 LS1 into my 1987 3rd generation firebird. The Control module and harness are from the donor car..... Basic mod for VATS removal and tach multiplier done with HP TUNERS.

I've done alot of research before asking this and I could really use some help. I want to use the factory tach but get zero responce. Using the 3 X multiplier on both and have the tach connected to the RPMl output which would normally feed the ebcm I have a nice square wave. I've tried a 10k resistor to power and watched it lift the voltage on the high side of the signal with no effect. Tried even grounding it using the same resistor with no luck. I verified the tach is operationable on a 1987 1/2 ton Chevy truck today and it was perfect. At least for what I was looking for. Thanks in advance....

Rick