Hey guys....been a while since I've had issues with the ole 2000 F150 Stepside Ext. Cab Lariat. About 3 weeks ago I had a spark plug blow out of the #4 hole while going down the interstate and had to hobble it about 30 miles to the shop to get fixed. Been doing fine ever since, except I noticed last weekend when riding around on the farm that the 4x4 wasn't working. I rarely use 4x4 and when I switched it in 4-Hi it didn't do anything. I was sitting still when I switched it, and I did hear the clicking under the dash like the relay does, but nothing happened after that. No lights, no engagement or nothing. I put it in Neutral and tried 4-Lo and it didn't even click that time. I put it back in 2-Hi and tried 4-Hi again.....nothing at all this time, even no clicking. I have tried it again yesterday and it will make the clicking noise (like a relay or something) like it has always done, but no lights or no engagement. Also, the clicking comes in about 6-8 seconds after I move the dash switch....a little longer delay than it used to be. What gives???

I've read several threads on diagnosis, and have read the Factory Service Manual Diagnosis too. From my symptoms, is there anything in particular I should look for to save time and effort on diagnosing it? Also with the Factory Service Manual diagnosis, how am I supposed to complete those steps without a way to check the trouble codes that requires use of a NGS tool since I don't have one?

THANKS!

 

https://www.f150online.com/forums/19...diagnosis.html

MGD

 

just throwing this out there... I recently had my exhaust manifolds done. When I attempted to put it in 4wd, it didn't engage. All the clicking was there. I traced it to a vaccum line/connecter that runs under the battery. The Mech. forgot to reconnect it. I followed the vac lines from the 4wd cylinders and picked it up there. On my truck, that line/connecter runs under the battery tray so it was hard to just see and it took some tugging and prodding to find it. p0171/0174 codes came up as well, so it was vac leak for sure....I ran that truck for at least 6 weeks with that connecter unplugged before it threw the codes. I was also able to hear the vac leak with the truck running. It's worth a shot before going through that whole diagnosis process presented on the video (which of course I did before finding the missed connection).

Always remember if something is wrong with your truck and someone other that you has worked on it, look in the general areas where the work was done. This may reveal missed connections etc.

BTW: It's a great video if you want to learn about your 4wd system

 

Well....I watched the video and immediately started troubleshooting. I first started with the fuses under the drivers side knee panel, and then checked the fuse box under the hood. I didn't bother counting fuses, as it was all working before and there should be no reason a fuse would be "missing". I used the continuity function on my multimeter and every fuse under the dash and hood beeped....meaning they're good. Right?

Then I moved to what the video said do. I checked the voltage at the solenoids with a Test Light (with the ingnition on). Both solenoid harness plugs had constant 12v power. The 2wd solenoid was grounded when the switch was in 2-Hi. I then went and switched the 4x4 switch to 4-Hi.....got the clicking noise from the upper center of the dash, then no lights, no engagement. Now the ground should have moved from the 2wd solenoid plug to the 4wd solenoid plug, per the video. I had no ground on the 4wd solenoid. I rechecked the 2wd solenoid (while switch was in 4-Hi), and it still had the ground at it's plug.

I ended the test there since there was obviously an issue. What does this mean though?

I did one more thing to check it....I unhooked the battery and let the truck sit for 30 minutes. I then reconnected the ground on the battery and started it up and tried to put it in 4-Hi. I got the same symptoms as before. Just the clicking noise in the upper center of the dash with no lights, or no engagement.

 

You done good so far but now up but up against not knowing how the system works in total.
First, removing battery does not reset this system as there is no memory that has to be refreshed or cleared.
.
Back to the system; your up to the transfer case motor operation.
This is the point the relay clicks because the motor is not able to run to it's first position. The motor is located on the rear of the transfer case.
It moves one position to turn a rod to engage the transfer case to transmission. At the same time has moving electrical contacts that forward connect out of the plugup to the firewall solenoid so vacuum can operate the front axle actuator. At this point the dash lamp comes on for 4H.
.
For 4L, the case motor turn one more position to engage the lower gear ratio, at the same time changes the transmission shift points due to the lower speeds then the 4L comes on.
.
Check for the motor operation as the next thing.
If it does not operate, be sure the electrical plug is seated, then remove the motor for inspection and testing.
The relay clicking is the GEM keeps trying to operate the motor. The GEM has over sensing circuits that releases and retries the motor.
Just as a side note, the GEM controls power windows and also uses current sensing should anything prevent window closing.
Good luck.

 

Did you miss the part about where I said that there was no ground on the 4wd solenoid when switched to 4-hi ? Re-read that part. I feel like the issue is up to that point, but don't know what it means.

 

Lets put it this way; it's my interpretation of where you are with the issue based on my knowledge of how the system works.
I am not going to spar with you about what you did or said.
You do not need factory service info or test equipment beyond a voltmeter, knowledge of the system and decision making based on observations.
I provide system info to help you, not to debate it.
Good luck.

 

so you're saying I need to check for Transfer Case Motor Operation based on the info I've given you? Where is this motor located and I will check it next.

 

Look in reply #5 where is says "The motor is located.........................
Good luck.