On an automatic the gear select connector that plugs into the trans gear position switch has 6 pin outs as such.
A-Blk/Wht (grd)
B-Orn/Blk (goes to D16 on ECM)

C-Dk. Blu (back up light)
D-Lt. Grn " " "

E-Ppl (continuity)
F-Tan/Wht "

A/B is for ECM input.
B/C is for Back up light.
E/F is to prevent starting in gear.

What is the actual function of A/B? What does the ECM do with it?
Reason to know: The LB9/MD8 (5.0TPI/700R4) will be installed in my hotrod, but the transmission shifter is a Lokar floor style with it's own P/N switch. Obviously my set up does not include a P/N switch mounted on the trans like the F-body did.

What are the ramifications (if any), if A & B are not used? Thank you in advance.

 

park/ neutral switch circuit closed in park or neutral A-Blk/Wht (grd)
B-Orn/Blk (goes to D16 on ECM) the ecm will raise idle speed when this circuit is closed.

 

This is for the motor I have in my other thread "91 TPI running outside of car", in which your help is appreciated. OK, that sounds reasonable. So if I hook up a toggle switch between these wires to simulate P/N or IN GEAR (like I have for the Starting circuit), the idle RPM should change accordingly. I'm I thinking right? Thanks.

 

yup

 

That's awesome. Thanks again tunedperformanc.

 

Ya, it did just that. Thx.