Brooklyn

Hello, I am installing an after market tach on my 1991 HB truck. The manual says to splice into a white wire on pin 2 on the ECU for the rpm signal. Well I took off the seat and am looking at the ECU, but there seems to be several white wires coming out of the ecu. Does anyone know how to tell what wire to tap into?

Thanks!

Brooklyn

Turns out is was the White/Green wire, which is the 3rd pin on the second square section of wires.

Z_Rated

According to the 1991 Factory Service Manual "pin 2" is the second wire in the second block, top row to the left of center. There are 14 pins in two rows of the second block.

Is that the same? What color is that wire?

Z

Brooklyn

That wire is indeed white, but the tach doesn't work when connected to it. When I connected it to pin 3, the wire next to it, the tach work. That wire was white with a green stripe.

Z_Rated

Cool, just letting you know what I found out for you. Enjoy your truck, I did. Z