I'm glad to have found this message board. I found some great (and familiar) content on hear.

On to my problem:

I began having a problem using 4x4 LOW in my 1999 B4000 about two years ago. At first, when in 4WD LOW, and coming to a stop, the system would shift into 4WD HIGH, and then back to to 4WD LOW, on its own....thats the strange part. The first time it did this, it would toggle back and forth when coming to a stop, repeatedly.

The problem went away for a while, until recently. Now it will not engage into 4WD LOW at all, unless its REALLY cold out out...and even then, as soon as it is in, it toggles back to 4WD HIGH and stays.

The fact the it toggled pretty much rules out a problem with the transmission range sensor, right? And it seems as though the symptoms of my problem would rule out a problem with a speed sensors (4WABS).

Using an ohmmeter, I tested the switch and it checks out.

So, I'm thinking its either the sensor plate in the shift motor mechanism or the GEM, but their both expensive enough to replace, that I'd rather not guess.

BTW, 4WD HIGH has always worked fine, and still does.

Does anybody now how I could go about testing these components on a 1999 B4000? Does anyboad have any other ideas on this one?

Thanks,
Chris

 

I'll bet the problem is with your shift motor on the transfer case. Mine gets hesitant like this sometimes too if I don't use it much. Problem is, the motor gets dirt and grime around it after a while and then one day when you go to use it it's stuck. Frequent use should fix the problem, if not you may have to see about removing the shift motor and servicing it. Keep that baby clean and loosened up and usually they work OK.

 

Welcome to FTE!!

 

Thanks for the replys. I'm thinking its the shift motor as well, but I'd be pretty psyched about finding some info somewhere that could help me prove it with an ohmmeter. I'm a geek, what can I say?

Where's the best place to find part numbers/buy Ford replacement parts on the cheap?

Thanks,
Chris

 

Well, my worst fears have been confirmed: After replacing the shift motor, the problem still persists.

At this point, I'm pretty confident that it's probably a bad ground somewhere. The reason being, that my cruise control has been intermittently quitting, and at night, the dashboard lights will just go out for a minute or two and then come back on. This truck is whacked!

If anybody has any other ideas, clue me in. Thanks.

-Chris

 

You probably have a bad GEM module.

 

03EDGE has a point....the GEM plays a very important role in process ...to get a better idea of how the 4x4 system works on your Ranger, read the following (compliments of Racerguy):

...The ['98-'00 Ranger PVH] four wheel drive system is an electronic shift 4X4 system that allows the operator to choose between three different modes. The operator can switch 4X4 HIGH modes at any speed. To engage or disengage 4X4 LOW the vehicle speed must be less than 5 kph (3 mph), the brake depressed, and the transmission must be in NEUTRAL.

The shift motor sense plate, an integral part of the electronic shift motor, informs the generic electronic module (GEM) of the transfer case shift motor and contact plates A, B, C and D position.

The digital transmission range (TR) sensor is located on the LH side of the transmission, and informs the GEM when the transmission is in the NEUTRAL position.


The electronic shift motor is mounted externally at the rear of the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4X4 HIGH, 4X4 LOW and 2WD range positions.

When the GEM verifies the completion of the transfer case shift from 2WD to 4X4 HIGH (reading the contact plate positions), the GEM will then energize both pulse vacuum hublock (PVH) solenoids (supplying ground for 45 seconds). The PVH solenoid will allow a HIGH flow of intake manifold vacuum to the "wheel end hublocks", engaging the wheel end hubs to the front differential and transfer case to achieve four wheel drive.

When the GEM verifies the completion of the transfer case shift from 4X4 HIGH to 2WD (reading the contact plate positions), the GEM will then energize only one (low vacuum solenoid) of the PVH solenoids (supplying a ground for 10 seconds). The PVH solenoid will allow a "LOW" flow of intake manifold vacuum to the wheel end vacuum hublocks, disengaging the wheel end hubs from the front differential and transfer case to achieve two wheel drive.

The 4X4 shift motor uses a module containing two relays which, under control of the GEM, shifts the transfer case shift motor between 4X4 HIGH, 4X4 LOW and 2WD modes.

The solid state clutch relay is used to activate the clutch within the transfer case which aids in shifting to 4X4.

 

Here is what the problem was:

The computer was not getting a +12V signal from the brake pedal switch. Stupid me....i figured if the brake lights worked, then the switch was good.

After a new wire (faulty wiring harness..who'd a thunk!?)was run from the brake pedal switch to the GEM, all is good.