1998 Ranger Won't go into 4x4 Lo

[PNW Ranger]

Hello:

Scanning through this forum, I think I have a fairly typical issue. 1998 Ranger, Splash Trim. Automatic Transmission, 3.0 Liter V6. This trim has a knob to control 4x4. Knob easily switches into 4x4 High and the dash light comes on. However, when in either Neutral or Park, and with foot on brake, the 4x4 Low light does not come on when knob is turned. And when driving, the vehicle does not act like it's in 4x4 Low.

What should I have my mechanic look at?

Thanks
PNW Ranger

 

[RonD]

Automatic has to be in Neutral, not Park, for 4low
And yes foot on the brake pedal pushing down

In 1998 you should hear a relay "click" behind the radio when you change the 4WD system to any setting
Listen for it
And do you hear it when 4low is selected?

If 2WD to 4high and back is working then shift motor on transfer case is working and all fuses for the system are OK
GEM module, behind the radio, is the 4WD Controller in 1995-2000 Rangers
And its working if you can shift between 2WD and 4high

If you don't hear a "click" of the relay when 4low is selected then it could be a few things
With engine on, shift to Neutral
Shut engine OFF
Try to restart engine in Neutral, if starter won't activate then Neutral switch is not "showing" Neutral to Computer or GEM so no 4low
If you can restart engine in Neutral then neutral switch is OK

1998 should have a column shifter interlock, it locks the shifter in Park unless brake pedal is depressed
I assume shifting out of Park is not an issue?

Brake pedal switch is actually 2 switches, has a brake light switch and a brake pedal sensor inside, the sensor part is what is used by the GEM to allow 4low shift
The sensor side uses Fuse 9(7.5amp) in cab fuse box(1998), you can check that fuse but its most likely OK if interlock works

Long shot is the dash 4WD switch, these never break..........................but never say never, lol
The switch is just 3 resistors and 2 wires(2 more wires for light inside)
The GEM sends it a fixed voltage(5volts), depending on the switch position a lower voltage comes back to GEM
The selected position passes the fixed voltage thru 1 of the 3 resistors
Return voltages are
4volt, switch in 2WD position
3volt is 4high
2volt is 4low

I would expect a failed switch to cause 4WD lights to Flash, flashing 4WD lights means "trouble" in the system, i.e. if shift motor fails or shift motor position contacts fail, the GEM would flash the 4WD lights when you selected a new transfer case position
And you don't mention that

 

[PNW Ranger]

RonD:
Thanks very much for this reply. Working from the top:

n 1998 you should hear a relay "click" behind the radio when you change the 4WD system to any setting
Listen for it: YES, GOING FROM 2H TO 4H AND 4H TO 2H.

And do you hear it when 4low is selected: NO.

Try to restart engine in Neutral, if starter won't activate then Neutral switch is not "showing" Neutral to Computer or GEM so no 4low
If you can restart engine in Neutral then neutral switch is OK: YES, ENGINE WILL START FROM NEUTRAL FOLLOWING THIS PROCEDURE.

1998 should have a column shifter interlock, it locks the shifter in Park unless brake pedal is depressed
I assume shifting out of Park is not an issue? SEEMS TO WORK NORMALLY.

I would expect a failed switch to cause 4WD lights to Flash, flashing 4WD lights means "trouble" in the system, i.e. if shift motor fails or shift motor position contacts fail, the GEM would flash the 4WD lights when you selected a new transfer case position
And you don't mention that. 4WD LIGHTS DO NOT FLASH.

The next thing to check seems to be Fuse 9, I'll replace that today.

Thanks much.
PNW Ranger

 

[RonD]

From responses I would say its a GEM issue or dash switch issue

Unhook one battery cable
pull out the radio
GEM will have 4 multi wire connectors
18 pin
26 pin
16 pin
22 pin
Unplug each and then plug it back in, that's to clean the contacts, pin and plugs

The 22 pin connector is for the 4WD system
Unplug it again
Pin 8 will be a white/blue stripe wire, that goes to the dash switch

Also unplug the 26 pin connector
Pin 21 will be a Grey/red wire(there are two grey/reds on this connector, pins 7 and 21)
21 goes to the dash switch

Put ohm meter on the grey/red(21) wire and the white/blue wire(8)
These are the 3 settings for switch
3.9k ohms
1.1k ohms
360 ohms
Move the switch and OHMs should change to one of these 3 values
Its "ohms" so won't be exact, its basically "in the ballpark" when testing ohms on anything

If you are only getting 2 different ohm readings replace the switch
The GEM is not getting the 4low "message"

If you get all 3 and they are "in the ballpark" then GEM is most likely the issue

 

[PNW Ranger]

Looking like it might be the GEM. If I wanted to replace the GEM, where would I find one?

 

[RonD]

1998 to 2000 GEM from Ranger or Mazda B-series, these are only years that have the speedometer interface
Also needs to match your options
i.e. power windows, power door locks, 2WD or 4WD
If you can get the part number off the GEM label that would be best, take a picture of it

car-part.com

Part needed is "computer box, not engine"

1998-2000 GEM is programmed for "tire rotations per mile", this is set for stock tire size for that vehicle, it can be changed
So if the speedometer is slightly off with new GEM then it can be reprogrammed using Forscan, a free to try software

 

[PNW Ranger]

Thanks, what I'm seeing on carparts.com that looks close is an "Engine Control Module" by A1Cardone. Remanufactured. Looks like different programming's for different options.

Thanks

 

[RonD]

Car-Part.com--Used Auto Parts Market

www.car-part.com

You need to select "computer box, not engine", from the parts list

Then your zipcode

Then Search

Next page select Multifunction 4x4
Then Search

As said if you have the current part number use it in the above selection

 

[PNW Ranger]

Yes, I see now. I was on Carparts.com.