98 Chevy PU, door locks

Grab an injector wire for tach.The locks probably reverse polarity.They suck a little.

When he said grab and injector he meant,  if you look at the fuel injectors on the engine you will see a 2 wire harness plugged into each one.  What you want to do is look at the wire colors in each of those plugs.  One color will be the same at each of the plugs.  To get the tach wire splice into one of the other wires.  For instance for the sake of arguement say the injector harnesses have the following colors.

#1  Pink/green and Red      #2 Orange and Red   #3  Blue/white and red  #4  Gray/white and red

In this case you would hook into either the pink/green, orange, blue/white, or gray/white wires since they aren't common to any of the injectors.  It doesn't matter which one you tie into just go for the easiest one to get to.  Hope this helps.   As far as the reversing polarity door locks if you search the relays section there's a diagram that tells you how to hook it up.

You can get to the wires at the Driver Door Boot between the Door & Kick Panel

Cut LOCK  & UNLOCK Wire in Half.

Relay 1

LOCK:

Relay 2

UNLOCK:

It's not " whatever ".....You need to be sure before proceeding.....

Without OEM Keyless Entry .........Reversal Rest At Ground Door Locks