what's this to and where does it connect

[imtonydillard]

Re 1990 D150 3.9L

This harness is under the dash on the driver side. The wire colors are: Blue white, Yellow red, White green and Brown red.

Any idea what they go to and where the receiving connector might be located?

http://s58.photobucket.com/user/imtonydillard/media/wire_zpscmlk38rt.jpg.html?sort=3&o=0

[PToombs]

Here it is,

[imtonydillard]

Pete - I don't understand your response.

[PToombs]

I copied the tag and posted your pic right on the page so it can be seen without going off site.

[imtonydillard]

thx

[thrashingcows]

I don't know for sure but wonder if it is for a factory tach?

[PToombs]

Factory tach plug is gray and flat, not squared.

I just went and looked at my truck and thought I didn't have it, and realized I do, it's fastened to the hood handle bracket. I think it's the diagnostic plug for the ABS system.

[cougar]

According to my FSM, it says "RWAL Test Connector (In Plant Use Only).

[PToombs]

Yup, thought it was after I looked at my truck.
I never bothered looking in the FSM because I wasn't sure where to look to find a random connector under the dash.

[Lazyjoe1]

Do they still make an aftermarket tach that will plug into my factory 93 harness? Thanks in advance. Joe

[Richie O]

Do they still make an aftermarket tach that will plug into my factory 93 harness? Thanks in advance. Joe

Isspro did. They still might.