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I have been having all kinds of problem with my vehicle, the thing is starting to drive me into the poor house. It has about 160K on it, truth be told if it would stay problem free it would be a great vehicle. So here are the two problems i am having and I am hoping there is some affordable DIY fix. My 4x4 wont engage, when I try to engage it I hear a clicking it sounds like its coming from the drivers sided near the back of my head. The 4 hi light will come on but vehicle does not engage. The second problem is that I had a code pulled and it says vehicle is running lean anything that you can recommend looking at on this would be great. Its running good but drinking fuel like crazy. The last thing is I cant shift out of park without reaching up into the steering column and pushing the override button. I think this might be the switch on the brake pedal based on what I read on here this morning. The people on this forum have really helped me out over the years, I just wanted to say thank you.
Since the 4WDHi light is coming on, it sounds like the transfer case is going into 4WD. That would leave the front differential failing to engage. You might have to test for vacuum down at the differential to see if you are getting vacuum to the actuator there.
The lean code is probably because of a vacuum leak. Both problems could very well be related...fixing one might fix both.
For the shifting issue, check any and all fuses related to the brake/stoplamp switch. Like fuses 2 and 5. Did you check to see if your brake lights work?
Break lights are functioning properly. I will check the fuses tonight. Where would I look for the vacume leak? I have attempted to engage the four wheel drive, even though the light comes on its not engaging at all. Is there some sort of control module on the drivers side of the expedition maybe in column between the two doors, I hear a ticking noise that sounds like its coming from there when attemting to engage.
The ticking sound is the 4WD relay module and is normal. Look under and around the battery for a broken vacuum line.
There are two points of engagement for the 4WD system. One is where the transfer case engages the front driveshaft. The second is where the front driveshaft engages the front differential. From the sounds of it, the transfer case is engaging the front driveshaft, but the front differential is not. The front differential has a vacuum controlled actuator that pulls a lever to lock the front differential to the front driveshaft. If the vacuum is not reaching this actuator then the front driveshaft is powered and turning, but is not engaged to the front axle...leaving you with just rear wheel drive.