Yes and yes. My Schematics do not show the resistors in any part of the circuit. I would assume they are there to keep the points from arking but I cannot be sure.

 

Hey JMC, I see, which makes sense because if my guess is correct, one or both of the resistors or the relay internals themselves are fried causing the erractic back anf forth un commanded shift. I just got a brand new ford relay module in, I disconnected battery, and cleaned blew out and electric greased the terminals on this new module, truck is all back together for now, but i still am going to perform diagnostics on the old module and see what the DVM says. That will take some setting up and wiring to perform, but I am anxious to see the results and I'm sure you'll be interested too.

 

Let me know what you find out.

 

Do you still need 221 ?

 

 

Hey guys, unfortunately its back. SOB!!!!! I've replaced the relay module, shift motor, ohmed and cleaned the dash switch, had the truck scanned by computer, which oddly pointed to the new shift motor as being a problem. No GEM codes......what do I do now?

Heres what it did tonite, went to snowy lot, tried 4x4, worked flawlessly, driving home went clikc click uncommanded shift to 4x4high, switch was in 2H. OK, got to driveway, tried to shift to 4L, it did but it shifted to 4L in the 4H position on the dash switch, no response except when it is moved in or out of the 4H position, which takes it into and out of 4L, in 2H it remains in 4H. I crawled under truck, wiggled and tugged on wires to no avail. My dad thought the shifts sounded rough, but I always thought they sounded "clunky" WTF? Is the gray rotary sensor on the back of the shift motor out of wack somehow? Is there an adjustment that can be made to it like a calibration? I don't think my dash switch is bad if I ohmed it out ok.

Just can't believe I'd have a bad motor new out of the box from NAPA.

Any advice is greatly appreciated.

Bless you gurus!

 

Found this online TSB 01-14-1 : Electronic ESOF Transfer Case - Inadvertent 4X4 HI or LOW Shift Events

3. False Input to GEM A false mode switch input on circuits 682 and/or 780 (Dark Blue) could be interpreted by the GEM as operator requesting a 4H shift. Under this condition, the GEM will command shift motor movement to match the false switch input. The red 4X4 indicator will illuminate just as if operator moved the switch. If the condition became intermittent, the 4X4 range and also the indicators could switch back and forth between A4WD/2H and 4H.
a. Check the Mode Switch circuits between the GEM and dash for chafing, shorts, crimps, continuity. Repair wiring if faults found or if wiring okay, replace the Mode Switch itself.
b. After any repair, pull DTCs from the GEM (even if there are no DTCs available). Clear any codes present and cycle ignition.


Just wondered if that would be an issue. Its acting like a short to me but I cannot find any bad wires. Where do the wires from the transfer case motor up into the cab go? Under the carpet? And where does the dash **** wires go? They seem to disappear into the dash.

Thank you

 

The wires are routed from the transfer case along the top past the transmission up the firewall on the passenger side to the main engine harness. Those wires cross over the fire wall under the cowl to the driver side where they cross the bulkhead into the cab. From there they go to the different components in the dash. Follow the wires from the shift motor to the engine compartment looking for melted sections near the exhaust or rubbing that may have worn through the insulation. Sometimes when transmissions are serviced the wires get pinched or moved and this happens.

 

Hey JMC, I went through the wiring today as much as I possibly could. Took lower dash off, traced wires from 4wd switch, unwrapped them from the factory tape and checked for cracks/rubs/pinches. None found.

But I did find on the grey pin connector to the back of the switch, the darker blue of the two middle wires was loose within its connector, as if the little plastic tab holding it is gone. Would that possibly be an issue? I made sure it was all connected well.

Continued checking all wire harnesses in the cab and underneath truck. Nothing abnormal was found. Shifted truck many times in shop in and out of 4wdH and 4wdL. No problems present. Started up truck after putting back together and UPON START UP, it did the uncommanded shift. But, after messing with it, it came out of it and I went on my merry way for a 10 mile test drive. Tried 4x4, worked fine.

I think I just need to take it to a Ford mech and have a complete diagnostic ran. Could this be GEM/switch/relay related and NOT show up on a scanner?

 

Now how would you know that ? I mean, having the trans sitting on the concrete about 15 different times wouldn't have anything to do with it, would it ???



You know what wires I had to replace, - right there at the harness Y, where it branches. I think that might be where your referring to ? Where it's buttoned to the top of the trans right by the block with one of those white colored hangers taped into the harness. Surprisingly, I never had any problems, but by the looks of the harness, -a section of it anyway, - I should have had plenty of crap going on. I had bared, chaffed, smashed wires and the harness was full of dirt, oil and whatnot's.

This was in the 98, I had a new 01 Crown Vic harness handy so I just chopped, soldered and adhesive heat shrink-ed in new section. Not sure how it got that way. I noticed it when I removed the intake to service the gaskets. Also had to rewire the Trans sensor (Range sensor), that harness takes a beating as well.

NYfordguy, -JMC may have a different deal, being a stick and for some of what I have posted,-that's more less automatic specific. Just in reference to harness routing maybe, not sure. This is just what I have found in the past. Definitely follow what JMC posts, I would. You never know what your going to find. The problem might fly out at yuh or you may have to do MORE digging to find it.

 

If the pin on the switch was loose it could very well be the source of the phantom switching. The GEM relies on resistance to determine the position of the switch. If you have access to a code reader that can access the GEM pids for the transfer case then by all means get a reading. The codes start at P1804 and go to P1891. There are 20 or so codes. Your GEM might still be the cause.

 

Hey guys, thanks very much for the replies. Yes My wiring seemed to be ok, I mean my truck only has 41,000 on the clock, gramps never drove it much, so I find it hard to believe my wiring is shot somewhere or rubbed through. And a visual inspection revealed no red flags to me. My wiring acutally I think is routed to the drivers side firewall, if memory serves me.

Can you still get that little 4 pin connector for the 4wd dash switch? I probably should get a new one to cancel the possibility of that non-secured wire causing problems.

I think I'm going to bring it to the Ford tech i know and have him do a complete scan of the truck. Eliminate ANY possibility of wiring problems. THe computer knows all! (sometimes!)

But it still brings back another questions, this shift to 4x4high, thats caused by a resitance change in the switch yes? if the switch remains in 2H but the shift occurs, what exactly could be triggering that? Could it be the GEM/dash switch/ or transfer case motor, I don't think there a chance in all the world it could be the switch because it isn't even moving!?

 

The GEM is the computer that controls the electric motor on the transfer case. It relies on input from the switch, contact plates in the shift motor assembly, speed input, transmission position input and brake position input. If the GEM is defective it will cause erratic shifting. All of the inputs are monitored and if they seem out of the norm the GEM will set a code. Not all generic scanners will pick up these codes. The dealer will certainly have the tools to pull these codes, if any are set. One last thing to check are the grounds for the GEM. They are two on the passenger side and one on the driver side behind the kick panels. have a look at them to be sure they are clean and tight.

 

Hey JMC I found the 4wd connector on Rockauto

WPT417 part number $27 so I answered that question myself.

About these grounds, all on the inside of the cab behind the kick panels. Colored green I assume? Thanks I will def. be looking at these, removing, cleaning and re-installing them if possible.

 

There's two grounds behind that panel, -both are green. One you'll see right away, the other you'll have to look for. I get rid of the paint behind them and wheel the backside of the bolts.

There's one behind the passenger side KP as well. That might be the inertia ground, I can't recall. You might want to hit those two on the firewall, one is by your 4wd solenoid, the other is the engine to firewall ground. Both green.

Drivers -



Pass -