Chassis operation independent of body

Good morning.

Both Gem and air suspension modules are located behind the radio in the dashboard. Pictures attached.

Yes, you need the Gem module.

Roy

Which is which in the drawings? I see the location of the module in the second drawing in relation to the radio opening, where is the module shown in the first drawing in relation to the radio opening?

Which is the GEM and which is the air suspension modules?

I probably need to get part of the wiring harness too, so I will have the connectors and the wiring to sort out and follow for re-connection. do these connect to other items needed for their control?

Do I need any other electronic control modules? Is there one for the transmission, or one for the transfer case that I need? I want to make sure that I get all the modules from the body that I need for the chassis.

Thank you.

First one on the left is GEM, the other is the air suspension.

Both are behind the radio and close to each other.

You will need the harness inside the truck as well.

the transmission works off the engine PCM.

And it looks like I will need to remove the entire dash so I have full access to everything, especially the wiring harness as I do not have much access through the radio opening.

Do you know if the wiring harness is an 'all-in-one' or if there are separate wiring harnesses for some of the things I will not be needing? Would make it easier if there were separate harnesses to get what I need, but I suspect it is easier at the factory to put in 'one' harness which feeds everything, provided they either put in the correct harness for the correct vehicle to match the options, or that there is one harness installed and it is used as the options are installed?

It is an all in one harness.

Roy

That leads to one last question, from my previous question "or that there is one harness installed and it is used as the options are installed":

If I go to a 'U-Pull It' auto parts salvage yard and pull the harness from a 2000 Ford Explorer, that harness will have the connectors for the 4WD and the air suspension even though that specific vehicle may not have 4WD and air suspension, or would I need to find a vehicle which as 4WD and air suspension (there is a vehicle in a local 'U-Pull It' yard which as 4WD but does not have the air suspension).

Hopefully the "It is an all in one harness." indicates that a 'complete harness' is put in each vehicle on the assembly line to allow options to be installed during along the assembly line as specified on the vehicle manufacturing ticket. Hopefully, that will be a simple "yes." answer, which makes my choices on what to do easier.

Thank you.

The harness will depend on options. if it did not come through with air suspension, the connectors will not be there. you will need to find one with all the options you have.

Roy

That answers what I was wondering. I will pull the harness out of the Explorer body I have and hope to sell afterwards, they would need a different harness to match what ever vehicle that they will be putting the body on, if they do not just use the body for parts (the body is currently a complete Explorer body).

Thank you very much.

You are welcome.

I have a follow up question: I was told that I needed the GEM module, however, if the air suspension module in on the left of the radio opening (I have the radio out and the opening clear, the center console out, and the dash pulled down for access behind the dash) and that operates the air suspension; the engine PCM controls the transmission; with the transfer case being in default "Auto", and I have an 'Auto-4Hi-4Lo' switch which I will install to operate the transfer case to switch from 'Auto'' to '4Hi' or '4Lo' as I may need - what does the GEM module do that I would need it for?

The person who told me that I needed the GEM module may not have fully understood that I was completely removing the body and separating it from the chassis, so I would not need any 'body' controls, alarms, monitors, etc The person who told me I needed the GEM module was the Service Manager at the local Ford dealership, but then our discussion continued and he later made the comment 'Oh, I didn't know how much you were taking off and disconnecting.' - at the time I didn't tie that to maybe not needing the GEM module. The air suspension module, yes, that makes sense because the chassis has the rear air load leveling suspension.

I'm just trying to make sure I understand why I am taking what I am taking so that I will be able to connect things back up to operate the chassis without the body.

I won't need any: anti-theft, no alarms; lights (head/stop/turn/hazard/etc); no horn; etc; which would be controlled by the GEM and the body electronics. This is because I am putting the body of another vehicle on the chassis and that body will already have all those items self-contained within itself.

The only "connections" between that body and the Explorer chassis (other than body mounts) will be: 1) steering wheel shaft connection to chassis steering shaft; 2) brake pedal connection to the chassis brake system using the chassis master cylinder and vacuum booster; 3) accelerator pedal connection to the engine's cable; 4) transmission gear selector lever connection to the transmission shift cable; 5) parking brake connection to the chassis parking brake cable; 6) a battery positive connection to the body; 7) chassis ground connection from the body back to the battery. That will (basically speaking): power the body lights and etc, start the engine, drive the chassis, steer the chassis, stop the chassis.

There were four connections from the body down to the transfer case area from the floor under the driver's seat: one went to an air bag sensor on the driver's side frame rail - I don't need this one; one went to the transfer case; two went towards the back (I presume one is for the fuel pump, sending unit, etc; and the other one is for the air suspension).

With the engine PCM controlling the transmission, and I have the wiring harness from the engine compartment and the power circuit fuse box - all to reconnect the power circuits, engine, engine PCM, etc, back together by reconnecting the connections to each other and for the anti-lock braking system ...

What does the GEM module control that the chassis needs?

Thank you for your help in understanding what is needed and what it does.

GEM module controls the 4 wheel drive. The actuator and the switch. It is definitely needed for your project.

Roy

Thank you - I saved that image so I will know how the wiring to the GEM needs to be reconnected, and it looks like I will need to take the BPP too ... and what is the DTR (where is it located and what does it look like)?

Also, what/where does arrow B (S251) go to?

- I can connect up a 'Hot in Start', 'Hot In Run', and a 'Hot In ACC Or Run' as shown at the top left of the drawing, so no issues there.

- I can connect up a 'Hot At All Times' as shown at the top right of the drawing, so no issues there.

- I have the 4WD Mode Switch that I can connect back in, so no issues there other than what is that 'B' arrow showing to S251?

- Mine is A/T with 4.0L, so I can connect up the DTR ... if I knew what it was and where it was located ... so that is an issue I need to solve.

- And if I do the above ... then I don't need to try to remove the wiring harness which goes to the GEM, correct?

Do you have a similar drawing for the air suspension module showing what needs to be connected where? I may be able to save removing the wiring harness if I know what connects to what and I can create the wiring shown in the drawings - that would be great if you have that.

Thank you - this went from simply removing the modules to much more complex in trying to get the wiring harness, to maybe not needing the wiring harness if I can make my own to connect what needs to be connected (if I removed the wiring harness, I would remove all unnecessary-for-my-use wiring anyway).

DTR is on the side of the trans. it is the range sensor.

I still think you need the harness for it to work.

I will get the diagram for the air suspension

Roy

diagram

The DTR is likely in the wiring harness which goes from the transmission toward the engine, possibly to the PCM or around about to the connection to the fuse box and to the firewall connections (one of the two large wiring harness connections at the firewall which are then run inside the body to wherever/whatever the various wiring runs to.

Do you know where this goes in the drawing:

TO S251
DIA. 34-3

I suspect that is referencing location 'S251' on 'Diagram 34-3'?

there is no indication or wiring routing in my system.it is part of the main engine harness as well as the interior harness as well.

Roy

Thank you for looking.

You are welcome.

Roy

The above work getting the wiring harness has lead to another question: I traced 4 (maybe 5) of the wires in one of the harnesses which came up from the chassis through the floor under the driver's seat, over to the harness which runs along the driver's side from front to rear, and all the wires in those harnesses went towards the front ... except for those 4 or 5 wires ... which went to the back to what I can best describe as a 'relay block' (versus a 'fuse block').

Question 1: Being as those wires came from the transfer case/fuel pump/sending unit/air suspension (I don't know which yet - but the connections on the chassis lead to those items) ... do I need to take that relay block, and, if so, what would it be for?

- The relay block was next to the module which has the keyless entry code on it, and is basically in the jack compartment where the air suspension on/off switch is located.

Question 2: I followed the green with yellow tracer wires from the air suspension on/off switch and they go up to the rear seat, cross over to the passenger side, then go up to the 'A' pillar wiring, and up to the air suspension module. That indicates that I can just connect those two wires to the air suspension on/off switch and locate that on/off switch any place which is convenient for me to use to turn the air suspension off when I go to service/jack up the vehicle, correct?

Thank you.

Ok.

Question 2 is correct.

Question 1. take the relay block doe your project

That shows the horn relay, the horn relay is in the power fuse box / relay box in the engine compartment - I already have the complete wiring harness and associated stuff connections and things.

The relay box in question is mounted back by the jack - does it also have a horn relay (and PCM, starter, fuel pump, etc) relays?

Thank you

Let me see if I can find it

picture attached

Looks like those wires may be trailer tow, which I don't need.

That's the only relays I see in there which would likely go to the chassis.

Do you see any others?

nope, no other relay boxes anywhere.

Roy

Then I don't need that relay box either as I won't need towing lights for what I am doing.

Thank you.

your welcome

I was laying the engine compartment and dash area wiring harnesses out and found two more relay boxes: one which mounts to the support for the air cleaner; and one which was in the dash between/near the two modules I needed.

The wiring harness in the engine compartment, the end which goes to the right side by the air cleaner and where the blower was, the only connections I think I would need would be for the right front brake (anti-lock system?) and the cruise control unit (which I will be removing and will not need) - do you have a layout of the relays in the relay box which mounts to the air cleaner support mount, and do you have a diagram schematic for showing what goes to what for the engine compartment wiring harness?

Do you have a relay box drawing which shows what the relays are for in the relay box in the dash wiring harness, and what the connections go to for the dash wiring harness?

I am trying to eliminate what I do not need, and make sure that I do not eliminate what I do need (I am slowly laying out the wiring harnesses and trying to figure out the connections as to what goes to what and eliminate the ones I don't need).

Thank you.

found one under the hood

That's the power fuse box / relay box at the left fender near the master cylinder. The one I'm inquiring about is on the right side and mounted below / on the air cleaner support plate.