This will be somewhat lengthy so please bear with me. My son's Father in Law died and I bought his 1999 Ford Ranger that looks like new. It had 119,400 miles on it but the speedometer was not working. Previous to me buying it he had taken it to the Ford garage where he bought it. and $4,100.00 later and still no working speedometer.That price is not a misprint. Ford changed the speed sensor, rear end with a salvage yard rear end, wiring harness from speed sensor to dash, and another harness I cannot make out what it is. Anyway I still changed the speed sensor on the rear end but it did not fix the problem. So as I was driving I hit the gauge cluster with my hand and the speedometer worked intermittently. So I pulled the cluster and took it to a local shop that rebuilds gauge clusters. His opinion was the area where the wiring harness plugged in was not making good contact and he suggested I buy a gauge cluster at a salvage yard. I did and transferred my gauges and speedometer into the new/used gauge body. It would glitch once maybe every 50 miles but would start working immediately again. The truck now has 122,529 miles on it but the speedometer now glitches often and longer and sometimes I will get the hard shift because of no signal. So even though I thought this would not fix it I again tried a new/used gauge cluster from a salvage yard. I have tried it with both the original speedometer and both salvage yard speedometers with the same result, not working properly. So again even though I thought this was not the problem I changed the speed senor on the rear end with the Ford sensor the Ford garage installed but it did not help. The one I had installed was a NAPA brand. I looked closely at the harness plugs and they look fine. About the only thing I have not changed is the GEM module. Do these Rangers have a problem with the speedometer head acting this way? But then it would mean I have 3 speedometer heads that do the same thing. As stated 1999 Ford Ranger, extended cab, 4 wheel drive. So any help or ideas are welcome. I probably could buy a GEM module at a salvage yard but I do not want to throw parts at a problem when I am not sure what the problem is. I am a pretty good mechanic and have a high end Autel scanner that will give a health report plus allow me to manipulate different system but I don't think I saw a test for the speedometer on it. Bruce

 

Welcome to the forum

That was a high price for service that's for sure

1998-2000 Ranger used the ABS rear axle sensor to get a speedometer pulse count, you know this

So if the ABS sensor OR the rear axles tone ring failed then the yellow ABS light on the dash would come on each time you drove it
You don't mention the ABS light being on, so 100% not the rear axle sensor or axle itself

Yes, the ABS sensors 25,000ppm(pulse per mile) signal is spliced and sent to the GEM module, and to the ABS Module
GEM module converts that 25,000ppm to Ford's standard 8,000ppm signal, and sends it out to the Computer, Cruise Control and Speedometer on 1 wire

The Computer will set one of these codes if GEM is not sending out a good signal, i.e. disconnected from rear axle sensor or just broken GEM
P0500 Vehicle Speed Sensor Malfunction
P0501 Vehicle Speed Sensor Range/Performance
P0502 Vehicle Speed Sensor Low Input
P0503 Vehicle Speed Sensor Intermittent/Erratic/High

Have the codes been read?
These codes may or may not trigger the CEL(check engine light), usually will though
No P0500x code mean valid speed signal is present at the computer

If you have cruise and it woks then rear axle sensor and GEM are OK

So we have gone through the troubleshooting the first shop should have done, lol

Now pin 1 GEM module has a Grey/Black stripe wire which is Speed Signal OUT
And this wire has at least 3 splices, one for the computer, one for cruise(even if you don't have cruise), and one for speedometer

So if there is no P050x code, or cruise works, then I would have to say the Splice for the speedometer's grey/black wire is bad, why hitting the dash worked, lol
But easy fix
YOU can splice in a new wire to the GEM's working grey/black wire and run it over to the cluster

Just look for the grey/black wire on Pin 1 of the cluster 12 pin connector, cut it so you can add a new wire
Run that wire to GEM module and splice it to the grey/black wire also on pin 1

Use the cluster of choice

 

It has aftermarket cruise control ( Rostra )that drops off when the speedometer glitches. I did not cut into any wires near the GEM module but picked up the VSS signal under the hood as the truck was factory wired for cruise control, just did not have it. But the glitch occurs even if not using cruise. ABS light is off and no codes. When I first got the truck P500 codes were present but none now. Now on this truck on the right side of the dash behind the radio is the ABS module even though I do not have ABS . Some sources were claiming this converted the VSS to a usable signal for the computer. Is there any truth to this? My ABS is part number F29F02C018-AD and there are many used ones available for little money. Is this worth trying? From what I can see I take out a screw accessed through the glove box and then the module slides over to remove. I actually drove the truck with the radio trim panel removed and when the speedometer bounced I jiggled the wires on the GEM with no change. I also carefully looked at the pins on the speedometer head and receptacles the speedometer and gauges plug into for any sign of corrosion but none is present. And the ABS light is good as it lights up for a few seconds when the truck is started. And when I first got the truck the OD light was flashing due to no speedometer not working but now the glitches are short enough that it does not come on. Really puzzling is that it worked for 2,600 miles after my first repair. I knew the man that bought this truck new very well and when he told me Ford wanted to change the rear end because they claimed it had too much play in it I jacked the truck up while he watched checked it and told him it was normal but he trusted the Ford dealership more than me.

 

All Rangers had rear ABS 1990 and up, so you have RABS in 1999 you could also have 4wheel ABS(4WABS)
Only the 4WABS would have a converted speed OUT
4WABS module is in the engine bay, seen here: https://www.ranger-forums.com/attach...10226-1819.jpg

Can't miss it, 5 brake lines

So no, if you have rear ABS then no speed signal there

No P500-503 is odd especially if OD light was flashing when speedometer stopped working

So it may be a faulty GEM module or GEM module ground
Only 1998-2000 Rangers had GEMs that can do speed conversion
GEMs also did 4x4 control and power window/door locks

If you want to look for a used one, try here: https://www.car-part.com/
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GEM is call multifunction box by wrecking yards
Pick one that matches your vehicle
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And no GEM doesn't do Keyless entry need the RAP module for that, as well as GEM with extra hook ups for it


Speed sensors generate their own voltage, AC voltage, 0.5vAC to 8vAC, the faster the tone wheel spins the higher the voltage
But the AC Voltage is not used directly
AC voltage is a Sine Wave, goes to say +4v then to -4v and back to +4v, that pulse is what is used
But system only uses half the wave, the + volt half
So one of the wires on the rear axle sensor is a ground, grounded at the ABS module and GEM
The + volt wire is what is used as the pulse per mile, which is why there is only the one grey/black wire OUT to computer, speedo and cruise, because each of these components has its own ground the other half of the signal
So a bad ground at the GEM could effect speed signal,

2000 GEM has same wiring as 1998/99

 

I believe the reason the OD light was not flashing this time is because the speedometer failures are now mostly drop down to 0 and then bounce right back to correct speed. When ordered this truck he ordered it with roll up windows and manual door locks so it has none of that. Now one time about two weeks ago the OD light started flashing because the speedometer went down for about 1 mile. There was a code for VSS signal at that time. I erased the code so as I work on it I can see if any new codes come up. I would be better off if the speedometer was not working at all as then I would know if what I am doing is the repair or not. Thank you for the information. If I ever get it fixed I will post what the fix was to help other people.

 

Here is another parts site I use https://www.partshotlines.com/. I hope it helps someone.

 

You can do this as a test as well
Unplug the rear axle ABS sensor and go for a drive, yellow ABS light should come on within a few minutes, just to confirm ABS system is monitoring rear axle sensor
And it was working when plugged in

While rear axle ABS sensor is unplugged you can use a jumper wire to short both wires together then go to GEM connector, unplug it and test the red/pink(pin 9) and green/black(pin 18) for 0 ohms or continuity, to see if both wires are OK from ABS sensor to GEM
Move GEM wires in dash around to see if there is a intermittent connection

 

I disconnected the connector at rear ABS and after 50 feet the ABS dash light was on so it is sending the signal to the front. My GEM module is a hard one to find as the last two letters are EC. In fact a few salvage yards told me there was no such part number but I have found one locally for $60.00. I wanted to do the testing you suggested before I bought it. Now the red/pink and green /black you want me to ohm which connector are hey on. I have one connector on the bottom of the GEM and three connectors on the left side as I look at it through the opening. The last thing I want to do is ohm the wrong wires and possible short something out. Being this GEM is so hard to find I may just buy it. I am also having a slight problem with the 4 wheel drive. It would have nothing to do with the front hubs as I converted them to manual hubs. I am glad I did as the first time this happened and it was stuck in 4 wheel drive but I turned the hubs out and was able to drive home. Every once in a while when I try to switch from 2 to 4 or back again I get the lights flashing on the dash and then I need to pull the fuse and reset the module rather than wait for it to reset. I thought the problem was the transfer case motor so I purchased one from a salvage yard but still get the problem once in a while. And for those of you looking for a transfer case motor new you will have a very hard time finding one. Cardone sells them new but it is out of stock until January 2024. Cardone does have rebuilt but I have never had much success with rebuilt Cardone products. Dorman will seem like they have a new one but you need to look closely as it is for an electric Ranger and not gas. Anyway the only reason I mentioned this is because the GEM also controls the relays for the transfer case motor and possibly I do need another GEM module. One las thing CarParts.com does have a new transfer case motor but the brand is Replacement and I have no idea of the quality but I may be forced to try it as there are no other ones new available.

 

On the connector that plugs into the bottom I am seeing a green/black wire on the outside left pin and on the right side outside pin I see a pink wire but do not see and trace on it.

 

Its called Connector 224(C224), has 18 pins/slots, as per diagram, pin 9 and pin 18 have the ABS sensor tie in

 

I installed the new/used GEM module but it must be bad because it reads 80 mph at 10 mph. I scanned it with my Autel scanner and it had 10 different faults in many due to VSS and speed sensor that I was not seeing with my old one. Unsure if I should try another one at this point or what. Man at the salvage yard is seeing if he has another one but the main problem is he seems hesitant to offer a refund.

 

Yes, automotive electronics is hard to get right when NEW, used is even tougher
Any GEM that starts with F8(1998), XL(1999) or YL(2000) should be OK to try
Middle number is always 14B205

You are correct the last digits are the revision and matching those IF THE SAME YEAR is best, but "EC" in 1999 is not the same as EC in 1998 or 2000

 

Yes I found that out. All the number on this one matched mine and my truck was built March 1999 and other on June 1999.

 

I found the correct wires to ohm and they checked out. Reinstalled old GEM module and back to correct speed again with still some glitches. Does anyone have any experience with the rebuilt ones ( GEM Module) online for $190.00? I have ysed Flagship one a few times for the main computer on a Crown Vic and a Tahoe and they worked fine but they do not offer this module. Thar brand replacement transfer case motor was delivered by UPS and it goes into 4 high quickly but a little hesitation going into 4 low, I hear the relay click 2 times before it goes in. I still have a new Cardone unit ordered through Summit and expected ship date is January 1st, 2024. Anyway unless I find a good GEM unit I seem to be unable to do anything more at this point. Even if the GEM is not the problem it is hard to cross it out without having a known good one to try. And Ford changed two different wiring harness, the rear end with a used one, rear ABS sensor, and supposedly did something with the gauge cluster and still had no working speedometer. So at least I am doing a little better than Ford did. And I got most of the paperwork with the truck so if anyone thinks I am kidding with what Ford did I can scan and send you the proof. The only thing missing is the bill for one of the wiring harnesses. I may explain thigs a little too much but if anything I have done so far can help someone else I want them to get that help And RonD without your help I would not be at the point I am now. as I don't have the Ford repair manual or disc plus even though I am a good mechanic I believe you probably know these Rangers inside out. And for those wondering why 4 wheel drive is a must in the summer for me here is the story. I do not off road with this truck and it would be a shame to do that. There is no rust on the truck and it still looks great. But I heat with wood and the wood I am cutting is at a friend's house 80 miles away. This summer had been very wet in Pa. and I need 4 wheel drive to get back in some areas. Even though this truck is small and cannot haul what my 3/4 ton truck can it gets 19 mpg on the turnpike and I am up there every weekend anyhow. So I am using it as truck without beating it up. I just hop I figure this problem out. Any ides just tell them to me and I will check it out. I amy need to put a zipper on the dash though as I am in there quite often.

 

Have you opened up your GEM and had a look inside?

Google: Cleaning Ford GEM Module

And it could simply be a cold solder joint on Pin 1 or 9 or 18
So once the case is off look at where those pins connect to the circuit board and touch each with hot soldering iron to reflow solder

 

I will give that a try. I forgot to say the defective salvage yard module was reading mph in reverse when I backed into the garage.

 

Electric speedometer could show speed in reverse, its just an electric motor that gets a speed pulse, no longer a reverse spinning cable, lol
Not sure how they disable that, but in most vehicles it is disabled
I would think the AC sine wave is there/generated regardless of the direction of rotation of the tone wheel, same pulse per mile forward or backwards
Interesting question, need to look at how Variable Reluctance sensors send out that pulse, might be a clue there

 

And maybe because the speedometer was reading way high. Usually on this truck my mph does not read until I get on the road. It was showing 75 mph as I backed into my garage.

 

Slow down!!!

LOL

 

Okay I have been thinking about this and now I have a question. Is 4WABS or RABS more common in these 1999 Rangers? The module I bought at the salvage yard had the same exact numbers and even had the Pick Up Electronic 4 X 4 on the sticker and there is only a few months difference in build dates. But what happens if that truck had 4WABS and mine does not. This would send an unfiltered signal to that GEM and possibly cause the way too high reading. Or does the XL5T-148205-EC differentiate that this vehicle is a RABS version? I need to know this so I can also use that modifier when looking for a GEM Module.

 

It should have been XL5T14B205EC I had an 8 instead of the B in previous post.

 

Just look in the engine bay, for the large unit near Master Cylinder with the 5 brake lines, can't miss it, if you don't see it then you have RABS

GEM module and ABS/4WABS have no cross connections in any year, except Master's brake fluid level to turn on red brake light if brake fluid is low

4x4 references 4WD, and from 1995 thru 2000 the GEM was also the 4WD controller

Explorers used the 4WABS module(in engine bay) instead of the GEM to convert rear axle ABS sensor into the 8,000ppm, never ran across that in Rangers but Rangers used the same 4WABS module so it had that capability but need to be programmed for tire size
Explorer GEMs did not have the speed conversion circuit/software since they used the 4WABS module for that

Ford Part numbers break down this way
Up thru 1998 first 2 digits are the year
E9 = 1989
F6 = 1996
F8 = 1998

3rd digit was model of vehicle, 7 = Ranger/Explorer
4th digit = department at Ford that is responsible for this part

In 1999 this changed
First digit was year
X = 1999
Y = 2000
1 = 2001
2 = 2002

2nd and 3rd digits were now the Model
L2 = Explorer
L5 = Ranger
4th digit is still department


The Middle number is the actual Part Number in all years, didn't change in the 1998/1999 switch over

GEM module used 14B205 in any model Ford in any year it was used
If you Google: ford 14b205
You will see GEMs for many years and vehicle models
End digits are revisions and in this case can be circuit/software designation

XL5T-14B205-EC

1999 Ranger(XL5) part
GEM module(14B205)
EC circuit/software revision

 

Okay thanks, I thought maybe the other truck had 4WABS but mine definitely does not but with your information it does not matter anyway.as it did make a difference . Mine was ordered without too many extra frills, no power windows/locks, basic radio, no cruise, and uncarpeted interior. The salvage yard after considering it overnight refunded my money. There is one I found for sale off a wrecked truck so maybe that is a good try as at least the truck was running at the time. Rebuilt CarParts.com is selling supposedly rebuilt units for $190.00.

 

I bought a GEM module out of a wrecked1999 Ford Ranger and the speedometer works fine now. Then once I knew had a good Gem module I opened up my original GEM module and using an eyepiece like jewelers and coin collectors use I found a cracked solder connection on 2 of the pins. I soldered those and my GEM module is also good now so I left it in and now have a spare module. If I ever doubt that module I now a known good one to try. And over the weekend the transfer case motor I bought from CarParts.com worked great. If it is a good long term solution I do not know but for now it shifts the transfer case very well.

 

Good work

Thanks for posting the follow up and FIX