4wd lights flashing...intermittent

lesleb · Jul 27, 2016

1995 Ranger super cab, 5 speed manual 3.0 liter six. My 4wd lights flash 6 times then repeat but not regularly like every 10 seconds or so. Sometimes, but rarely, they don't flash and the 4wd system works. I cannot find any diagrams or troubleshooting aids. My Haynes manual has zero info on the 4wd system. Being that it is intermittent does anyone know of any common ground or vacuum line issues. I do not know if my system even has vacuum lines. I am up in Maine and there is a lot of rust on this truck. When it worked I changed my auto locking hubs to manual locking hubs. Thanks for any help.

lesleb · Dec 7, 2016

Solved...sort of.

I got zero replies on this thread. Not sure if I entered it incorrectly or something. A friend got me a troubleshooting flow diagram that wasn't an exact match and I got a schematic from O'reilly Auto Parts. The color coding of the wires seemed to be consistent with the schematic so I did some resistance and voltage checking.

At any rate I now almost know what it is. It might be the Generic Electronic Module (GEM) or the Powertrain Control Module (PCM). I removed the radio and part of the dash to get at the GEM and PCM. Not finding anything obvious I out it back together and it worked. Next morning it didn't work. Couple days later I took it apart again, cleaned contacts and VOILA, it worked. Next day it didn't work. I took it apart again and re-soldered about 80 to 100 pins at the printed circuit boards (PCBs) (going to the 4 plugs) of the GEM and PCM and it worked for 3 days then failed again.

Then I went a little further and re-soldered more component level parts on the same PCBs and it has worked for almost 2 weeks. Now I know it is either the GEM or the PCB. Neither of these seem to be available at parts stores but maybe it won't fail again.

RonD · Dec 7, 2016

Never saw original post but have a read here: http://www.therangerstation.com/tech_library/4wd_control_module_95-up.html

1995 was first year of the then "new" system

There is a 4x4 module that is basically just two relays that reverse polarity on the transfer case shift motor.
There is also a Clutch relay for transfer case clutch.

Inside the shift motor(on transfer case) are multiple electrical contacts on a wheel that turns with the motor.
These contacts "tell" the GEM where the shift rod in the transfer case is, i.e. 2WD, 4Hi, 4Low.
These contacts can get corroded and make and break contact which confuses GEM, and confused GEM = flashing 4WD lights

Look in this thread: http://www.explorerforum.com/forums/index.php?threads/how-to-rebuild-4x4-shift-motor.123542/
It has pictures of the disassemble shift motor and the contact wheel and contacts

As you surmised the GEM is the controller for the 4WD system in 1995
PCM(engine computer) is not involved in the 4WD

Here is a PDF for wiring on 1995 4WD system

pjtoledo · Dec 8, 2016

is 2000 the same schematic?

RonD · Dec 8, 2016

Looks to be almost the same

Tedybear · Dec 9, 2016

Had the same issue(s) with our '95 exp. We even have a couple of spare motors and sensors now for a backup.

Likely as Ron said the wiper switches need to be cleaned up and make sure they are not damaged. They need a bit of grease on the contacts (Dielectric grease, very very thin coating) when put back together.

Other issues: build up of metal shavings/worn material hanging off the sensors in the transfer case itself. You'll have 2 small roundish black "plugs" with wiring, held in by 1 fastener. Remove fastener and gently 'rock/twist' to remove the sensor. It's a tight fit with a sealing ring. You'll probably see a mound of what looks like powdered metal flake hanging off each one. Wipe clean and reinstall with a light coating of Mercon ATF (helps it go in better) While you're at it? Pull the fill plug and make sure the fluid is okay. Again, if memory serves, this uses Mercon ATF and not gear oil.

Theory behind the sensors getting gunked up is that the GEM system while in 4wd checks for speeds of both front and rear drive shaft outputs. If the signal isn't being clearly picked up-then it will dump out of 4wd and start flashing the light 6 times for the error.

Most likely it's the contacts as Ron mentioned. But sense your already playing around with motor contacts-It's not overly hard to pull the motor itself and remove 1 at a time the sensors and clean them off. (The one for the rear prop shaft is easy. The one for the front is buried a bit.)

S-

4wd lights flashing...intermittent

lesleb

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