99 F-Body LS1/T56 swap into 04 Miata complete except for getting Miata tach to work. Wired in 2.2K ohm resistor to "pull up" voltage as instructed in Flyin Miata's instructions, but get no response from Miata guage. Connected up aftermarket electronic tach to check signal from PCM and it does drive that tach, albeit at about half the rpms it should read. Wondering if there might be a tach setting in the LS1 PCM that needs to be changed. Anyone else run into this problem?

 

I solved my tach problem and want to post it in case someone else makes the same mistake. The Flyin Miata instructions and the 2004 Mazda wiring manual correctly called out the green with orange tracer as the tach signal input wire to the Mazda tach at the instrument cluster. However, there are two green wires side-by-side in the connector at the cluster. They look like a green with yellow tracer and a green with orange tracer. After digging further I noticed on the diagram that there is no green with yellow tracer called out, but there is a green with red tracer wire (cruise control). Bottom line: I had mistakenly ID'd the tach wire (green w/orange tracer) as a green w/yellow tracer (no such wire) and had mistakenly ID'd the green w/red tracer (cruise control) as the green w/orange tracer. In my defense, the "orange tracer" tracer does not look orange at all - it looks yellow. After swapping the wires the tach works perfectly WITH NO PULL-UP RESISTOR! Thanks all for comments and maybe this'll help someone else

 

This is a mistake I would have done. Thanks!