e38 Tach output RPMs too high (LS3 swap)

[benji808]

2013 Camaro LS3/TR6060 swap.

Running tach output from pin 48 with a resistor pickup for the signal. I get signal, but it reads too high. I had high and low resolution set at 6, but it was reading approximately 2x what it should have been. I then read that 6 is for 4 cylinder and 3 is for 8 cylinder so I changed to 3 but now it's approximately 4x what it should be, so maybe I went the wrong direction?

Screenshot attached, any guidance appreciated!

24886

[nonnieselman]

What tach are you using?

[benji808]

It's in a 1986 Jaguar XJ6 - so 6 cylinder tach.

[nonnieselman]

How did the car get original tach signal?

[benji808]

It's a digital tach. I have tach signal already, I'm trying to get the right output from the ECM to get a directionally accurate signal to the dash. I think it will be 9/10 or 12/12...may just have to experiment and see what gets me closer.