98 ranger 4wd low light stays lit - Ranger-Forums - The Ultimate Ford Ranger Resource


Drivetrain Tech General discussion of drivetrain for the Ford Ranger.

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  #1  
Old 09-30-2016
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98 ranger 4wd low light stays lit

Hi I'm new to the forums and I have a 1998 ranger 3.0 and recently it had both the 4wd lights flashing and after testing the shift motor and the switch, 4wd low light stays on. The shift motor works if I connect it directly to a battery. And I've tested the switch with a multimeter. It works but it won't go into 4 wheel drive and only the 4wd low light is on and its just on and not flashing. What is the problem here?
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Old 10-01-2016
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Welcome to the forum

Most likely a GEM issue, Generic Electronic Module(GEM), this controls cab electrics, and 4WD lights and shift motor.

Inside the shift motor is a wheel that turns as the shift motor turns, this wheel has 5 contacts(well 1 Ground and 4 contacts), when motor turns, these contacts open and close, that is how the GEM can tell what "gear" the transfer case is in.
And GEM activates the dash lights accordingly.
In this thread there are pictures of the shift motor and contact wheel inside: http://www.explorerforum.com/forums/...-motor.123542/

So could be the wheel is bad, or the GEM.
4WD lights flash when GEM gets confused, like if it closed the motor power relays and contacts didn't change, so no movement from motor.

When you turn on the key both 4WD lights should come on, that's the GEM powering up.
Does that happen?

There is a 4x4 shift module, it is just 2 relays in a box usually in with the GEM behind the radio,
The shift motor is a DC motor, so it can spin clockwise or counter-clockwise by reversing the polarity, +/- or -/+
That's what the 2 relays are for, the GEM uses them to turn motor in the direction to get the "gear" selected.
GEM "knows" what "gear" transfer case in by contacts on that wheel.
If this relay module was bad then motor wouldn't move, and if motor was stuck in 4Low position the 4Low light would stay on, but lights should start flashing if you selected 4High or 2WD because GEM wouldn't see contacts changing, motor not moving.

Here is the wiring diagram for 1998 Ranger 4WD
Always check fuses first, test them with meter, eyeballs are for pretty girls not fuses
Attached Files
File Type: pdf 98 4WD shift control.pdf (56.6 KB, 18 views)

Last edited by RonD; 10-01-2016 at 12:05 PM.
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  #3  
Old 10-10-2016
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sorry for the very late reply, the gem does power on and everything. its now flashing both 4Hi and Lo, also with a check engine light that is read as cylinder five misfiring and engine running lean. not sure if thats the problem or not. the transfer case motor still does move at all. also, would a gem modual in a 4 liter work on my 3 liter?
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Old 10-11-2016
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GEM module is for Cab electrics so engine size wouldn't matter.
Options matter, i.e. 4WD, power windows, power door locks, ect.....

A misfire can cause Lean code, so fix misfire in #5 then reset codes.
No, that wouldn't cause the 4WD lights to flash, they are flashing because shift motor isn't working

Lean code means there is too much Oxygen in the exhaust, O2 sensors can only detect Oxygen
P0171 Lean on Bank 1 means passenger side O2 sensor is detecting too much oxygen
P0174 Lean on Bank 2 means Drivers side O2 is

When a cylinder misfires then none of the oxygen is burned, it is dumped into the exhaust pipe, so O2 sees too much oxygen.

The engine is never running Lean, computer is adding more fuel, the CEL and code is to let the driver know there is a problem to check and fix.

If you get BOTH 171 and 174 at the same time then that indicates a different problem.

Last edited by RonD; 10-11-2016 at 09:51 AM.
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Old 10-14-2016
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I did get both at the same time but after i disconnected the battery to see whats wrong the engine light disappeared after the next start. oh and the ac compressor does not kick on at all, does this indicate a GEM issue aswell?
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Old 10-14-2016
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GEM doesn't have any connection to AC that I can see

Here are the 1998 Ranger GEM wiring diagrams I have
Attached Files
File Type: pdf 98 GEM 1.pdf (58.4 KB, 15 views)
File Type: pdf 98 GEM 2.pdf (38.8 KB, 13 views)
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  #7  
Old 10-14-2016
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So the compressor clutch doesnt kick on at all, why is that? and so by what youre saying its the shift motor is that isnt working?
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Old 10-14-2016
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And how do I test the shift motor and the sensor to know thats the one faulty? Because if either of them dont work, it wont shift into 4wd right?
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Old 10-15-2016
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You would need to remove shift motor

If you look at the wiring diagram posted for 4WD control, you will see the Yellow and Orange wires are the Power wires for the shift motor.
Take a picture of where the shift rod is in relation to the motor, so you can move it back when you are done with test, assuming motor works of course.

It is a DC motor so if you Ground(-) the Yellow wire and put 12volts(+) on Orange wire the motor should turn, then reverse that, Ground Orange wire and put 12volts on Yellow wire, motor should turn the other way.


In the same diagram you can see the Yellow/white stripe wire is the common contact connection for the other 4 contact wires.
Hook an OHM meter up to that wire.

Then hook other OHM Meter probe to one of the other 4 contact wires and power the motor, you should see 0 ohms when that contact closes as motor turns the wheel, same for the other 3.


Remove AC compressor's clutch wires, use Volt Meter to test for 12volts with engine running and AC on, if you have 12volts then compressor's clutch(field coil) is bad.
If no 12volts then in the engine fuse box will be the WOT(wide open throttle) relay, pull it out and check pins for corrosion, put it back in, retest for 12volts at compressor.

AC compressor's clutch only gets power if both pressure switches are closed, use an OHM Meter and remove each pressure switch connector and test switch for 0 ohms(closed switch), if not 0 ohms then the switch is open, so no AC compressor.
You will need to find these switches they move them around year to year, but they will be the only 2 wire electrical connections on AC lines
Open switch can be lack of pressure or too much pressure, there is one of each switch on any AC system, or it can even be a bad switch.

Do NOT bypass switches, you will burn out compressor or blow out condenser, but you can insert a jumper wire to test if by passing this switch turns on compressor, so you would see if that switch is the only problem.

Last edited by RonD; 10-15-2016 at 09:31 AM.
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  #10  
Old 10-15-2016
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sorry I didnt read this in time, I got a gem module from the junk yard and when I start the truck the module clicks like a relay, this didnt happen with the original gem. so im assuming the gem i had was faulty?
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  #11  
Old 10-15-2016
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update. got a shift motor from the junk yard and now the 4wd works, and after testing the ac i found out no matter what it blows hot. Is this the blend door actuator broken? and the clutch does kick in, so i think ill recharge it with refrigrant.
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Old 10-16-2016
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Good work on the 4WD part


The Blend Door stops or allows air flow thru the Heater Core.
So after engine is warmed up turn on fan and temp control to Hot.
You should feel the Hot air coming out of selected vent
Now turn temp control to Cold
You should feel the temp start to drop as blend door changes and stops air flow through heater core
If temp doesn't change then Blend Door is the problem

Blend door is a common issue on Ford Trucks, from Rangers to F-350s


Diagram here of Ford system: http://www.ford-trucks.com/forums/at...ntid=517&stc=1

"Temp Door" is the Blend Door
Evaporator Core is the AC "cooler" core

Most of the "doors" are Vacuum controlled(vacuum motor), all except the Blend Door which is electric

Last edited by RonD; 10-16-2016 at 01:35 PM.
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  #13  
Old 11-29-2016
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sorry to revive an old thread. I think the blend door is the issue, the blend door actuator is working but the blend door isnt shutting at all. Also got an engine light when going up a hill or under heavy loads that reads P0174 confirmed and another P0305 pending which i looked up its i beileve is bank 2 lean and cylinder 5 misfiring. I havent seen or heard any vaccume leaks and the light only pops up under heavy load like a hill or a bad start up which i used to have a horrible battery. the exaust smells like gas when started up will check if it is still the same after warm. and the fuel economy hasnt been really up to standards is what i feel like.
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  #14  
Old 12-18-2016
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Hi, I'm new to the forum also. My 4 low and 4 high lights blink every so often since I did a 5.0 swap...I put the awd case in and the 4wd plug is taped up and secured. Can I disconnect the gem module or do I need to rip the dash apart which I prefer not to. My tach works but I do wonder if it is calibrated to v8 not v6? anyone with knowledge can u get back...thanks, good forum btw
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Old 12-18-2016
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Quote:
Originally Posted by rangerbill61 View Post
Hi, I'm new to the forum also. My 4 low and 4 high lights blink every so often since I did a 5.0 swap...I put the awd case in and the 4wd plug is taped up and secured. Can I disconnect the gem module or do I need to rip the dash apart which I prefer not to. My tach works but I do wonder if it is calibrated to v8 not v6? anyone with knowledge can u get back...thanks, good forum btw
Welcome to the forum

You will get answers here

But what you need to do is copy your post then clink on this link: General Ford Ranger Discussion - Ranger-Forums - The Ultimate Ford Ranger Resource

General discussions
Down a few inches from the top on the Left you will see NEW THREAD
Click on it
Now paste your question there and give it a title, like "4WD and GEM" or "4WD question"

First, people don't look at old threads like this one often so you probably won't get many responses posting here

And second, what you did is considered Rude on most, if not all, forums.
You are not answering the original posters, thread starter's, question
You are "high jacking" his question with your own, like interrupting someone and then changing the subject.

The fact this is an old thread doesn't really matter, new threads are free and you want your questions answered, and New Threads get every ones attention when they log in, so way better chance to get a good response

Tach isn't correct, some explorer tachs did have V8 switch on back of dash
GEM runs interior lights, power windows, door locks and wipers, so probably not a good idea to disconnect it
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