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Explorer OBD2 Harness Re-work

EFI Guy

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I'm going to start you all off with a little video. It covers the very basics of a harness re-work. I'll add a full write up here with pictures covering pin numbers, wire colors, etc...as time allows.


[youtube]RaY-9v-SO_0[/youtube]


Part 1.5

This is sort of a re-cap of part 1. It answers some questions I have been asked and goes in to a little further detail.

[youtube]WPhaelK-0sw[/youtube]


Part 2

This covers the firewall harness.

[youtube]RNKGlvkCdsI[/youtube]


Edit: I originally made this thread to teach you guys how to do your own harnesses because I stopped doing them for personal reasons. I also think it's helpful to teach more people about the Explorer system because I think it's better than the old Mustang system, and more readily available.

I am now back in the saddle and doing them again. Because of the time off I have a pretty long waiting list now for harnesses. Hopefully I will have a helper soon to make the waiting list a little more reasonable. I still encourage you all to build your own if you can. You can learn a lot in the process if you can make it through my boring videos, and you're likely to be up and running faster that way.

Current pricing is:

PCM flash only: $275 (shipped).Only takes a day or two.
PCM flash and firewall harness re-work only: $400 + $25 shipping.
PCM flash and total harness rework (unwrapped): $500 + shipping. (roughly $30 for non 4r70w and $40 for 4r70w)
PCM flash and total harness rework (wrapped): $600 + shipping (roughly $30 for non 4r70w and $40 for 4r70w).
Add a spare PCM flash for $200.
 
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EFI Guy

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To start I'm going to list some C115 connector wires to be aware of. I don't like listing pin numbers for the C115 because they vary and are sometimes just plain wrong. The one I will list is pin #33, if you have a red/white in pin 33 remove it from both sides of the C115. One side will go to the trans harness. This wire is not needed and only adds to confusion.

The others mentioned in the video for NSS (neutral safety switch) and reverse light wiring are:

Pink- NSS in. This is start signal from the ignition switch.
Red/blue (96-97) or tan/red (98+) - NSS out. This is start signal to your starter solenoid.
Purple/orange- Reverse light switch in. This should be wired to hot in run and be fused at 10 amps.
Black/pink- Reverse light switch out. This will provide power to the reverse lights.

Now if you are NOT running the 4R70W all of the above mentioned wires can be removed. If you are running the 4R70W then you can keep them in place and run them in to the cab, or you can trace them down to the transmission harness and de-pin them there if you already have those circuits present near the trans in your body harness.

The following are PCM pin numbers that can be removed if you have no use for their function. Keep in mind not all harnesses will have all of these pins used and take note of any foot notes (like***)before you pull wires. Any PCM wires not in this list MUST be kept!

EVAP:

A quick note about EVAP before I list the pin numbers. The Explorer EVAP is a complicated system with a couple of electronically controlled valves, and requires a fuel tank pressure sensor along with a fuel level input signal that is different from what any fuel level sender will put out. So, I don't recommend that you keep it.
However, I can change it to the same type of EVAP system as the Fox Mustang system which requires only a single purge valve to operate. The only problem is it has never been tested in a vehicle, but it does work on the bench. If you would like to be a guinea pig, you can wire pin 56 Lt green/black to one side of your purge solenoid and hot in run to the other.

12- Yellow/White
56- Lt Green/Black
62- Red/Pink
67- Purple/white***

Air conditioning:

Note, the way I'll show you to wire in A/C will remove the PCM control over the A/C relay so A/C will NOT be disabled during wide open throttle. You will still get the bump in idle speed when the compressor cycles. Also, if you are not running A/C you can use the A/C input for a high idle switch which can be handy for winching, on board air, etc...

41-Dark Green/Orange or Purple*** This is the power input to signal that A/C is on. Needs to be hot whenever the compressor is engaged. (This will go to your toggle switch for high idle if desired)
69-Pink/Yellow -This is the wire the PCM uses to control the A/C relay (removed using my method mentioned above)
86- Black/Yellow- using my method this wires goes to ground if using A/C or high Idle.

*** On later harnesses where pin 41 is purple, I like to put pin 67 Purple/white in its place. There is another purple wire that we will use so doing so can eliminate the duplicate color and avoid confusion***

EGR:

47- Brown/Pink - +++
63- Orange/ Yellow
65- Brown/Lt Green

+++ This is where I install the resistor on 96 (only) harnesses when removing EGR+++

VSS: See the flowchart below about VSS to determine if you need it.

33- Pink /Orange - VSS-
58- Grey/Black- VSS +

Misc that we have no use for:

14- Lt Blue/Black
19- Orange/Black
43-Lt Blue/Pink

The Following PCM pins I shouldn't need to list if you are following the video and starting at the transmission harness and working up to the PCM. But, I will list them as a sanity check.

Rear O2 Sensors:

35- Red/Lt Green
61- Purple /Lt Green
95- White/Black
96- Tan/Yellow

4R70W Transmission:

1- Purple/Orange
3- yellow/Black
27-Orange/Yellow
29-Tan/White- (Overdrive switch) Goes to C115.
37- Orange/Black
49- Lt Blue/Black
50- White/Black
54-Dark Blue/White
64- Lt Blue/Yellow
79- White/ Lt Green- (Overdrive Off Light)Goes to C115.
81- White/Yellow
84- Dark Blue/Yellow

Now let's talk about swapping in the 4r70w trans from another year. The most common is 96-97 guys wanting to run the upgraded 98+ trans. There are 2 things you need to be aware of when swapping the 4r70w trans.

1. Your transmission range sensor must match your PCM. 96 or 97-01. (There was some carry over of 96 in to the 97 model year so use the PCM codes I provide as a reference).
2. You must repin the transmission plug to match the year of the trans.

#1 is easy, just use the range sensor and harness that match your PCM.
#2 is also easy as long as you are going with the 98+ trans on an earlier harness. Just repin the trans plug and remove the 2 unused power wires. To run the early trans on the later harness you would need to add 2 power wires. ( I would use the rear o2 heater circuit wires for this).

ZtmAcJp.png


WKSCJEj.png


NOTE: Pin 4 on the 98+ trans plug will most often be blue/orange, not red.

This diagram is for a 3g alternator, the Explorer uses a 4g alternator. The only difference in wiring is the 4g does not have the white/blk wire. The charge light is completely optional, if you choose not to use one then you can just provide hot in run to the green/red to excite the alternator. Usually you will have a green/red at your original fender mounted voltage regulator that can be used for this purpose.

XAOOWEB.jpg



The diagram below shows how you should change the wiring at the solenoid to work with the Explorer starter. I recommend keeping a fender mounted solenoid especially with a later harness that has very small start circuit wiring. If you are not using the 4r70w then you can use your existing Bronco wiring to feed the S terminal on the solenoid. If you are using the 4r70w then the wire that you will use to feed the S terminal on the starter solenoid will either be red/blue, or tan/red depending on year.

nwQqmPP.jpg


This is a basic diagram of how I handle power distribution.

Cpbvz39.jpg


And here is some VSS tech:

GAvBmAy.jpg


jeJfoMM.jpg
 
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dukeflr

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Garry, your work and selflessness are top notch. Thanks for doing this and inspiring many of us to to the EDIS route.
 

NJBronco

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Awesome work. Answered a lot of my questions. I'm not quite ready to put my engine back in so I'm holding off until I figure out where to put the ecu. I don't think I want to extend every wire in the harness so I'm looking at the center firewall mount. You showed just bending the wire and mounting the computer upside down. Any affects with heat this way? Not sure how heat sinks and such are laid out in there


I'm running an m5od trans so I think I can just delete the trans connector all together. Just use the one 02 wire and the reverse sensor wire


I think the pin out you are planning on posting is what I need. Not sure what's in that harness as far the additional wiring. As in am I going to be running the reverse lights off the harness or is it just the reverse sensor wire and this harness just gives and easy way to get it into the cabin
 
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ren71

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This is great. Thank you for your services and contributions! class act
 
OP
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EFI Guy

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Awesome work. Answered a lot of my questions. I'm not quite ready to put my engine back in so I'm holding off until I figure out where to put the ecu. I don't think I want to extend every wire in the harness so I'm looking at the center firewall mount. You showed just bending the wire and mounting the computer upside down. Any affects with heat this way? Not sure how heat sinks and such are laid out in there


I'm running an m5od trans so I think I can just delete the trans connector all together. Just use the one 02 wire and the reverse sensor wire


I think the pin out you are planning on posting is what I need. Not sure what's in that harness as far the additional wiring. As in am I going to be running the reverse lights off the harness or is it just the reverse sensor wire and this harness just gives and easy way to get it into the cabin

I seen your post with some of those questions on my lunch break, so I edited the video to answer them before I uploaded it.;)

I guess I should have clarified a little better in the video. You do not need to mount the PCM upside down, it is just a little easier (less of a bend) and makes it look a little better IMHO. You still have enough wire there to mount it right side up. But you end up bending it 90* to get it towards the drivers side, and then a 180* bend to make the connector face the right way. It's kind of a pain but it works either way.

I don't think heat will be an issue at all. It was the first concern that came to me when I seen the first one mounted that way. But then thinking about it further, there are heat sinks on the sides of the case (part of the case) for the transistors on pretty much every Ford PCM. I have seen the PCMs mounted in every position imaginable in factory form. A lot of the trucks mount them on their side so that would put the heatsinks on one side under the transistors, while the other side had the heatsinks over. That leads me to believe that mounting position probably doesn't matter at all.

I also realized that my "temporary" placement of my PCM on the floor board of my Mustang (under black carpet) is now going on 3 years with the PCM upside down. Mounting one upside down in a all aluminium Escape PCM box has to be better at getting rid of heat than my "temporary" mounting under black carpet.

I have lengthened every wire to mount it inside before, not an easy task! The method I used was to cut the PCM connector off of a V6 Explorer. They are a little longer and got me about 30" worth of extension. I then de-pinned the entire PCM connector of the V8 harness and used those pins as if they were the seamless butt connectors in the video and soldered them to my V6 pigtail. I had to add a few wires since it was a v6, but I had no shortage of spares around here.

Running the M5OD will let you remove all of the wiring down to the trans except your front O2 plug. The reverse light switch is part of the transmission range sensor on the Explorer, which won't work with your M5OD. But you could keep those reverse light wires in the harness and just branch out for them like you do with the O2 plug. You'll just need to put the proper connector for your reverse light switch on the end of it instead of the TRS plug. You could add VSS wiring to that same branch if you are going to need it.
 

904Bronco

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Thanks Garry, Great Video!

Hope things are going well with the wife's Medical stuff... Continued Prayers to you both.

Doug
 

Sabas

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Hate to hijack , but Dave ehat vehicle did upper hose come from?
Sabas
 

Green_Bastard

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Thanks for the info Gary
I have a few questions on a 98 harness. If I'm removing the EGR, do I also remove the DPFE plug and the wiring going back to the PCM plug? Also, what wires can be removed between the C115 and the PCM plug?

Jim
 

JSmall

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In for updates as I will be doing this to a 98 harness soon.
 
OP
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EFI Guy

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Thanks for the info Gary
I have a few questions on a 98 harness. If I'm removing the EGR, do I also remove the DPFE plug and the wiring going back to the PCM plug? Also, what wires can be removed between the C115 and the PCM plug?

Jim

Yes, you can remove the DPFE plug as well. But, do not remove Sig RTN (grey/red) or 5 volt reference (brown / white) at the PCM. They are both needed for other sensors. So just follow them back to the splice and cut them there then seal with heat shrink.

I have filmed a couple of hours worth of video for part 2, but I have been too busy to find the time to edit it all together, life keeps getting in the way. I'm going to try and do it Sunday night since I think I'll have some down time. I'll try and post a list of the all of the PCM wires that can be removed then. In the mean time you're welcome to give me a ring to go over them. You still have my number right?
 

Green_Bastard

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I'll try and post a list of the all of the PCM wires that can be removed then. In the mean time you're welcome to give me a ring to go over them. You still have my number right?

Yes I do still have your number. If your available this weekend sometime, I'll give you a call. Just let me know what works best for you.

Again, thanks for the info. As always, its a big help.
 
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EFI Guy

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I didn't get the video finished, but I did add any wiring you might want to remove from the engine harness to the second post.
 
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