This may help other people with module problems. Yesterday I went to a U Pull It salvage yard looking for a trim piece for a Tahoe I own. I ran into a section with Ford Rangers and found a group of 1999 Rangers and decided to pull the GEM Modules to see if they would fit my truck even though I have a spare. I found two modules that matched mine, one was actually manufactured same year and month as mine and one was manufactured a little later in 1999. They were made in Canada which all the modules I have seen so far were manufactured in Canada too. So this morning I wanted to see if they would work. Both modules worked on everything except the speedometer was again maxed out when only doing 10 mph. I don't believe these modules are bad but what could cause the faulty speedometer reading? Again one of the trucks was wrecked and one was just rusted out. The only thing I know of with my Ranger is that even though sold new in Pa. it has California emissions but that should have nothing to do with the speedometer. The wrecked truck only had 49,000 miles on it and the windshield, doors, and rear window were all intact so there was no water damage. I don't know how but I am going to try and figure this out for my own satisfaction and to help someone else out. These modules are no longer available through Ford so used or rebuilt are the only options. I talked on the phone to a module rebuilder about the problem but he did not know what it could be and he suggested the ABS module but I guess he did not understand on this truck the ABS module does not modify the signal and if bad would also affect the good module. My truck looks like new and I will have it for years to come so I want extra parts. In fact I will soon be parking it in the garage for the winter so it does not rust out.

 

Don't know the answer for that, I am sure its out there if you got 3 1998-2000 GEMs that had the same reading for speed
In those years the GEMs are programmable for tire size, to calibrate speedometer, revolutions per mile(RPM) for tire size
GEMs have full time 12volt wires, maybe if they are left unpowered long enough they lose the RPM number

Just a guess

 

I have a very high end Autel scan tool that is like most of them based off an iPad
So with one of the modules I thought I would just go in and set the parameters but unfortunately it only had that function available for a Ford Ranger 2014 or newer. I will have to see if an update is available for a 1999 Ranger. I have talked to two different module rebuilders and neither one had a clue to what it might be. And I really do not know what speed it was reading as at what I estimate to be 10 mph it maxed the speedometer out. If I do figure it out I will definitely post on here.

 

Went through the receipts from Ford and they had also replaced the ABS module with part number F29Z-C018A-A yet when I look at the part number on the module it reads F29F-2C018-AD.

 

F29F-2C018-AD is correct

Only Ford number I found as F29Z-C018A-A came up with a picture of ABS module with correct part number, lol, seen here: https://m.media-amazon.com/images/I/...EgIL.SS700.jpg

Looks like a typo on receipt no 2, 2C018, added extra A

 

Yes I posted that because the Ford technicians who supposedly know what they are doing changed the ABS module at a cost of 416.00 plus 74.00 shipping to fix the speedometer and the ABS module has nothing to do with it. And this is one of the biggest car dealerships in my area. They sell Chevy, Honda, Hyundai, and Ford vehicles.

 

I had some time today s0 I hooked my scanner up to the Ranger. There is a test for the GEM where you can activate the wipers ETC to see if the GEM is operating correctly. There is one part for the speed where you can recalibrate the GEM for mph or kilometers. Also in that same function it will show the read out of what the speedometer should be showing at the present time, you can even drive to see how it responds. Anyway it was all done with a good GEM in the truck but one day when I have time I will try one of the GEM modules that read speed incorrectly to see what is showing. I did not try to manipulate any settings with a good GEM but with one that is incorrect I will try to see if I can reset anything.