1st off I'm new to the site and to be fully transparent my 99 is a Mazda B3000. I hope that's not too Taboo for the site. I have visited a few times for viewing and thought I had a log in but couldn't remember it so I'm all new again. 90% of the truck's usage is Hunting or farm related. Any ways here goes with my problem and what has been done to the truck.

1st off the Vacuum hubs were replaced years ago with manual lock ins.
The truck has had electrical "Demons" for a while with Dome light(pulled the bulbs) I think because it was staying on and draining the battery but that was years ago. Windshield wipers will activate on their own and sometimes not work when turned on.
4-Lo has not worked in years but the 4 Hi was fine up until last hunting season.
Brother in law replaced the Joints and Shocks about 2 years ago and pulled the transfer case motor. while on his rack He manually shifted the transfer case and said 4 Lo and 4High worked fine. He said it had to be electrical. Fuse is good.
Since then I replaced the selector switch on the dash hoping for a cheap fix.
Truck would not shift in 4x4 Hi or Lo last year. Tried it a different day and it worked in 4Hi. Fast forward till a few weeks ago and it would not do anything. No 4x4 lights no action at the T-case motor.
Neighbor is a retired Ford mechanic so I took it to him. He could get it to activate only when the Ignition switch was on but the truck was not running. We thought the most likely problem might be the transfer case motor so I replaced it with a Dorman Last week.
Now nothing. Wont light up any 4x4 dash lights. Wont engage the T-case motor. FYI- I jumped the new and the old to a Hot and both turned so it wasn't the motor.
I tried to include all the steps taken some of this may not be relevant. Any ideas on what I need to do next? Is there a way to test the GEM to know if that's the issue or keep throwing parts at this old truck? Like I said its my hunting machine so I need it functional asap. Any help would be greatly appreciate if any of you have been through this and know my next steps. I'm puzzled and wish I had a manual shift!!!!!!!!!!!!

 

Welcome to the forum

1994-2010 Mazda B-series use Ford Ranger chassis and drive train so not taboo here

1995 thru 2000 used the GEM as the 4x4 control module, also controls dome light and wipers.........................see where I am going, lol

But 1998-2000 GEM was unique since it was also the Speed Converter for speedo, computer and cruise, in these years the rear axle ABS sensor was used for "speed signal" via GEM

There are only 4 parts to these 1995 thru 2000 4x4 systems, earlier and later just had 3 parts, no dual relay box
Dash switch, never breaks
4x4 controller, GEM
Dual Relay box, behind GEM in dash
Shift motor, on transfer case

There are two 4WD lights on the dash, 4high and 4low, these should light up with Key on as Bulb test, like all the dash lights do
The GEM will flash these lights if you change switch position and shift motor doesn't move
You don't mention this so I assume GEM is the issue

Also wipers coming on or not working could also be a GEM issue
You didn't mention "Door Ajar" light being on with dome light, so could be a GEM issue

GEM is located behind the radio, dual relay box is behind it

When it was working the "click" noise you heard was coming from the dual relay box, GEM was activating one relay in the box to activate shift motor
If you don't hear the "click" then GEM is not activating a relay, if it was and relay didn't activate, GEM would flash the 4WD lights
If you heard a "click" then it was activated and if shift motor didn't move 4WD lights would start to flash

Since no flashing 4WD lights I would say the controller was the issue, not dual relay box or shift motor
You need to use a 1998-2000 GEM, can be from Ranger or B-series 4WD, engine size doesn't matter, also needs to match for power windows/door locks

Shift motor is just a 12v motor, like power window motor, with 2 wires
12v/ground it spins clockwise, window up
ground/12v it spins counter-clockwise, window down
The dual relay has 1 relay for each of the 2 motor wires
When "off" BOTH motor wires are grounded
So the GEM only needs to activate 1 relay in the box to change that 1 wire 12v
Or activates the other relay to reverse the direction the shift motor turns
2WD to 4high, 4high back to 2WD

The other 5 wires on the shift motor are position sensors/contacts so GEM would know how far to turn shift motor and where shift motor is at, at any given time with key on

 

Thanks Ron D for the info. I kinda thought GEM would be the problem but needed some confirmations. Great info Given! I want to make sure I address everything.
4x4 Lights were coming on with a key cycle and then it would shift into 4Hi before starting the engine. Now there is no Bulb check at all.
Door Ajar light has been on for several years even though the doors are shut properly. Im assuming this is also a GEM problem that is related to the Dome light.
From the info you provided I have eliminated 2 of the 4 possibilities and due to my ignorance I replaced the 2 least likely. The switch and the motor. Also the truck has manual Windows not power so those work just fine. LOL
From this info Im guessing my best move is to order a GEM. Thanks sir for your help. I will post an update when the GEM is replaced and maybe a pic of my ride. It has a few cool mods

 

If Door ajar light was also on that means the door switch is the problem, not the GEM

Common issue on Fords after 1995, the door switch is on the door latch, at the bottom, so over time rain washes dirt down into the door and door switch gets sticky and sticks CLOSED, closed switch means door OPEN to GEM

Some people have had temporary success in spraying WD40 into the latch o it runs down to door switch and gets it unstuck

You can unplug the 2 wire connector on the switch, but you have to take door panel off to do that, so at that point just replacing the switch makes more sense, so you get back Dome light function when door is opened

Drivers door is usual suspect but can be passenger door as well, no way to tell until you unplug the switch and see if door ajar light is now off

 

Paging RonD
Ordered the ebay GEM (used- they all were) and installed it tonight. Key switch did not show a light test. Cranked the truck and turned the switch to 4Hi and it immediately worked the relays( heard the click) and then the transfer motor engaged (heard the ping). It would not however shift into 4Lo when in neutral. I thought I would just cut my loses but when I pulled to the house from my shop I noticed it shifted funny. Speedometer went nuts and showed 80mph and the truck stayed in High gear. So what now? Did I get a bad module?

 

Yes, reads like new/old GEM has issues

1998-2000 GEM also runs speedometer

 

Good Grief, so my only option I suppose is to order another GEM

 

The 1998-2000 GEMs are, at best, 22 years old now

 

1st GEM had the correct part # but the speedometer went nuts. I put the old one back in which crazy enough has been working except for 4Lo. New one came in I ordered off ebay from a company called platinum auto parts 77. It had the wrong part # which I noticed right off the bat. Not the part I ordered. It was YL5T-14B205-EB not XL5T-14205-EC. This is getting tough on me to keep my patience. Plugged it in just to try it and everything worked except the speedometer again. Put the old one back in again and Im at square 1

 

Latest in this saga: For RonD
So i found a 99 in a junk yard a few miles from home. Bought the GEM it had the correct Part number that matched mine. When installed the 4Lo sill wouldnt work and the speedometer went nuts again. Here is my thinking. I noticed the Wiring harness in the middle on my GEM only has one wire (purple I believe) going to to the 3rd pin from the right on the back (from the harness) bottom row. Not sure of the pin # so if I had a diagram that would help. On the junk yard 99 I pulled from I noticed that the middle harness had 2 wires. Truck didnt appear to have any features in the cab different from mine but I could have missed something. Here is my question. That is 2 GEM's with the exact Part numbers that did the same thing with the speedometer malfunction. I guess its possible both replacement GEM were bad but could it be that my truck is just wired differently than most?

Also if all this were not enough I think I busted the radiator this weekend. I sprang a leak and boiled over. That junk yard had several rangers from 96-99. Will any of those radiators work on a 1999? Only reason I would use one other than the 99 would be if the motor has been pulled out of say a 97 making it easier to get to the radiator. So whats the word? This old truck has been mine since 2000 and had 12,000 miles when I bought it. Its never given me much trouble until now so I cant give up on "The Nugget". Its at 225,000 miles now and I hope to see 300K

 

Radiators should fit assume same engines
There were just 2 different "styles", single core for manual trans, no trans cooler, and Dual Core, for automatic with trans cooler
Although by 1999 most Rangers had AC so even manual trans had Dual Core most of the time

These used different shrouds so need to use style you have now
Used radiators can be trouble, lots of sediment at the bottom that will NOT come out

Don't have 1999 GEM diagram, just 1998 and 2000

RAP module is Keyless Entry, so if you have Keyless entry you will have extra wires on GEM