Hey guys i know this has probably been asked many of times before but what are those i belive four wire that are tied back on the driver side under the hood? Do they have power all the time or just when the key is on? Or could i be completly wrong?

Thanks,
-AJ

 

Four wires capped and look like they've never been hooked up to anything?

I also wondered what these were for. My guess was for some electronic option not ordered on my truck and these are just the extra wires from the universal wiring harness.

I'm sure someone here has the answer.

 

They are for use at owners discretion, to get through the firewall. They are not hooked to anything at the factory.

There is 4 more just like them under the dash. :-)

 

Where inside the truck are those wires located?

 

Look under the dash by the PCM. You should see them there. Thet may be tied back against the harness, but they are there.

 

Thanks guys for the help!

 

Nice photos, Ken!

It looks to be about six of them in one photo. Is that your number?

My 2000 has only four, two of which I've already used.

Pop

 

I've found those wires before, and traced them in/under the dash. i'm wondering, how can you make one of them, an isolated 12v 'switched' power, without tapping into an already 12v switched wire source?

 

The Red, White, Blue and Black wires are the four pass-thru wires. These are in place to keep from having to drill a hole through the firewall. They are all 14 gauge wires.

The other two wires are LB-YE for the PTO circuit and LG-WT for the tachometer signal. These come right off the PCM and are not pass thru wires.

 

You could wire directly into the fuse panel if you have an open slot. Or you can always add a fuse tap. If you are looking for a switched 12V power, look at the Auxiliary Idle Control circuit (AIC). The connector for it is under the dash right in the middle. If you are not using the AIC module it has switched power readily available.

Here is a picture of the connector and it's location. The view is looking aft towards the dash from the brake pedal. That is the lower dash cross brace you can see.

 

EDIT for clarity....(my first post was confusing...)

Marv, your truck should have two other wires. The first will be a Light Blue with yellow tracer which is the PTO enable circuit (to PCM). I usually find this wire in the main bundle that runs to the OBDII connector but it sometimes will be in the smaller harness running to the AIC connector. I've even seen it in both harnesses. (mostly on cab/chassis trucks...). I think the tach signal wire started in 2002 models but I am not certain of that...

Then you should also have at least one other loose wire, which is keyed power. it can be hard to find but should be with the customer access wires however I sometimes have had to dig for it in the main bundle that feeds the OBDII connector. In those cases, it usually will be taped to the PTO enable wire and might have a label that says PTO Control Circuits. Sometimes you can see a tiny length sticking out and other times you have to unwrap the tape to get to that wire.

At any rate, when you find the second wire...this will be 12v keyed power. On pre98 models, the wire will be red w/yellow....on 99-01 models it will be Light blue w/pink and on Kens truck it will be white/blue (02-04).

If you wire a switch between keyed 12v power and the PTO wire (Lt Blue/yellow) then you will have fast idle (about 1200 rpm) as long as your truck is in park, parking brake is set, foot off the throttle and off the brake pedal.

Here is a photo of my '01 which might help you find those wires. This truck is an XL so it's pretty isolated under the dash (not too many accessory wiring). My wife's '00 Lariat has a bunch of stuff so it's much tougher to find the wires (but they are in there).