4wd System Operation & Help Thread

You would not be the only one.
At least you are attempting to diagnose first.
Lots of guys throw parts at it, before trying to diagnose.

There nothing wrong with guessing, but only after you’ve exhausted all other options.

What’s worse is when you fix something, and have no idea how you fixed it.
I can’t stand that

 

I hate it too but if I’m being honest it happens a lot more than I’d like to admit, I like to claim skill but it seems to be nothing but luck lol

 

Don't feel bad, electrical is one of those things that many people have problems understanding.
I wasn't too good with it myself until about 8 years ago when I discovered Paul Danner's classes and learned about voltage drop, that a voltmeter reads difference in potential, and a test light can be used to test just about any circuit on a vehicle.

 

If it makes you feel any better.
I fixed a battery powered circular saw today.
It kept cutting off in the middle of a cut. Stopped all of a sudden. Just cut clean off.
I told my father, I believe your saw is messed up?

Who would have though that all I needed to do was replace the battery.

I will say, I had not used the saw much. And never had a battery go low.
But I definitely diagnosed it the “problem” prematurely.

 

On Thursday I had an Oshkosh tractor brought to me with a horn not working. Spent 8 hours trying to diagnose it, went in the cab and horn wasn’t connected at the button… I feel that level of pain

 

SlowIy making my way through this forum as a relatively new member, I would just like to say to the OP, this is an incredible piece of research and documentation on the inner workings of the contemporary Toyota E4WD system. I'm a child of the old school manual twist- lock hubs/xfer case selector lever systems on the floor group, and first-generation "electronic-engage" shift-on-the-fly system from Ford (+-1987) and Chevrolet (1989-ish). What an amazing dance this Toyota system performs to give the driver 4wd (and back again) to keep everything from imploding, clashing, or I would even add: exploding. I'm >almost< a believer! (manual vs "shift-on-the-fly). One tends to shift from " hard-liner" to "couch-liner" as the years go by. The early system in the my Chevy had problems with the vacuum-electric switch on the xfer-case. (supplied by Chrysler/New Process Gear I believe) and it failed every year the first time I needed to engage it. (the dealer replaced it no-charge every time)


"Thank You".

 

It's actually relatively simple compared to many other systems that use multiple potentiometer's, encoders, clutches, and speed sensors to accomplish the same thing, not as simple as a lever and some vacuum switches but then again not much isn't electronic these days.
The problem with Toyota's system is the inability to communicate with a scanner or generate fault codes so all tests have to be done manually with a meter or guess and hope to get lucky.

 

Re: "Not as simple as manual xfer cases, and vacuum switches, and levers: I sure agree! Those early shift on the fly system were very complex with electro-vacuum actuator switches on the early GM trucks that were a nightmare to deal with: they required a special slotted socket (like an oxygen sensor) and were on the top of the case at an oddball angle that required a universal adaptor because of the angle, and really a lift and an acrobat to R&R it. The mechanics would openly ridicule it and the dealer would swap it n/c. It essentially failed from non-use over the summer months. 4 years, four replacements for my truck. (Two out of warranty n/c.)

 

Well… almost as if it was meant to happen. Engine started sputtering really bad under acceleration and then randomly kicking back to normal. Seems to be a real gremlin now, took the day off work so I can actually diagnose this pos

 

I know it's been covered already, but I think you may need to revisit the grounds. A continuity check and wiggle of each circuit is recommended

 

Just remember, units are important. Ohms vs volts in this case (and switching to the correct setting on multimeter)

 

Well. I ain’t no mathematician but them suckers are lean af

 

Wonder what the fuel trim numbers look like

 

Lol motor is in some bad shape, so much blow by that the oil fill cap lifted off the valve cover. Further investigation required… 4x4 no longer a priority

 

That sucks man. Sorry to hear.

I’ve seen worse as far as Lean.
But those ground electrodes are nearly gone. Just changing the plugs should show a vast improvement.

Do you have a scan tool?
I wonder what the fuel trims are doing?

Also, with the amount of blow by you say you are having, you’d think there would a bit of a low compression issue as well.

Do you have a compression tester?

 

So…no idea what I did but I fixed the engine. I’ve never been under the valve cover before but every single bolt was hand tight, doesn’t explain the way it was running but I pulled every sensor on the intake and replaced it, also new ngk plugs and denso coils initially it didn’t make a difference but I just drove around the block and shes running better then ever, however blow by is still present but far less than it was

 

I wouldn't worry too much about blowby unless it's using or leaking oil.
Did you ever do the main ground checks.

 

I did not as my focus was getting it running right, now that’s done tomorrow I’m hitting the 4wd diag hard again

 

Those plugs look pretty normal color for a modern engine aside from being worn out.

 

Im just surprised they are so badly worn, I did those 35k miles ago