ct3400tw 2000 windstar tach issue

Hi I installed a ct3400tw into a 2000 ford windstar, everything works fine except for one small problem, when I go to program the tach I seem to be having trouble the starter drags just a little bit. I went into the procedure of flashing the hood pin, then I go into the cab step on the brake press the lock and unlock button at the same time, park lights flash, next I release the brake and start the vehicle, then what happens is the park lights flash as if I had stepped on the brake, so its learning to high of a tach signal therefore the starter drags. I am getting the tach signal off an injector and the brake switch wire is hooked up properly. Can you shed some light on my problem???