I have a 99 expy 5.4l 4x4 with the 4r100 tranny. The harness for the tranny started melting through on the header, wonderful Ford design. So due to current injuries from a triaxle accident I had to bring my wife's truck to my buddies shop. I hate having someone else work on my stuff friends or not. So I need to replace the tranny harness, no big deal figured the harnesses are a dime a dozen and I was wrong. After 3 months of searching I found one on eBay. It came in and it was in great shape. Dropped it off to have it put on an a week later I stop back and they tell me that the harness I dropped off has 1 less plug than the 1 on the truck. So I did some searching and apparently the harness I bought is for a 4x2 not 4x4. Wife's truck has the extra plug that comes off by the neutral safety switch and the main plugs are both 38 pin male end that are the big gray squares by the firewall. So my question can someone tell me or give me a diagram/pinout of the two harness so I can add the 2 pins to the harness I just bought. Any help would be awesome. I've searched all over the web an forums and all I can find are either diesels or a 42 pin plug or 7.0/7.3 engines, I have a 5.4.

 

1999 Ford Expedition Navigator Wiring Diagram Repair Manual 99 Truck | eBay


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As much as I appreciate the eBay link I can't wait to get that in the mail. Kind of urgent I get this done ASAP. That's y I asked for help here. But thanx again.

 

I'm not sure I got the correct pin out your looking for. Before I confuse the issue even more, can you give us the wire colors of the two extra wires your wife's harness has?


And when you refer to the neutral safety switch do you mean the BOO/BPP switch or the DTR?


(In Ford lingo, the "BOO" is the Brake On/Off switch, later called the "BPP" Brake Pedal Position switch, and the DTR is the Digital Transmission Range switch.)

 

DTR and the colors are greenish with white stripe and pink with a black stripe

 

Here it is. Dont mind all the wires in the background. Im sitting on my old sportster as i work on my wifes harness.

 

I only found one 38 pin connector (C172) in the diagram. Are you sure both are 38 pin or did you count just one and assume the other one was the same?

Here is the one I did find:

 

My info shows two different DTR connectors for the 4R100, one for 4x2 and one for 4x4. Strange thing is they both show identical pin outs and wire colors.
And no wire matches the colors you described. Where does that connector pictured in your hand connect to?


The 38 pin connector (C172) alloro posted has pin 19 PK/BK and pin 20 PK in the Male half of the plug and pin 19 and 20 of the female half are indicated as "Not Used".

 

Yea a 38 pin plug. Identical plugs visually both have 38 possible pins to them. The one from my wife's truck however only had 32 wires where the one I bought had 28. But i actually just finished making the harness. I ended up just taking both harnesses down to a bare harness. All tape and wire loom off. Traced all wires to corresponding pins on each plug. Found the 4 wires I needed took them off one added them to the other. I had to swap the DTR plug from the only one to the new one cause two wires from that were missing on the new one and took the plug from the old one that was all together not there on the new one. Added the 4 wires to the main plug soldered everything together, rewire loomed and taped everything back up. Hopefully good to go. But just for future reference the difference between the 4r100 4x4 an 4x2 harnesses is the 4x4 has pin 23-24 and 26-28. 23pink w/black 24 green w/white is a separate small black plug and 26red w/white 28black goto the DTR plug.

 

Here is something that may effect your issue.
The 4x4 DTR connector pin 8 has a RD/WH wire that runs through the 38 pin connector (in on pin 26, out on pin 26) and goes up to the GEM. And the DTR has a BK wire that goes to ground. The DTR closes this circuit when in neutral, as the GEM will only shift in or out of low range if the transmission is in neutral.


I don't know if this circuit exists in a 4x2 model.

 

I think you got it.


I'm guessing that the 4x2 and 4x4 DTRs work differently internally, and that's why there are two different DTR connectors with the same pin outs, again I'm guessing, and that the 4x2 connector probably won't connect to the 4x4 DTR and vise versa. Maybe some one can chime in and confirm or deny?