Yet another 4WD problem...

cpark_12

cpark_12

New member
I've held off on posting this as I've been doing all the research I can, but I haven't found anything.

So, the other day I went down the road to cycle my 4LO and Center Diff Lock like I normally do about once a week. I went off road, put it in neutral, switched to 4LO, everything went smooth and it locked in in a second or two. Good! So, I pushed the CDL and it locked in in about a second or so also. Everything is good! So I climb a hill, drive around in the mud for a bit, then I throw it in neutral and unlock the CDL, it unlocked just fine. I put it back in 4HI and this is where the problem starts...

I hear the actuator shift the transfer case into 4HI, but the 4LO light is still flashing on the dash. Well, I turn the switch back to 4LO and nothing...The light stays lit up like it is in 4LO, but it definitely was not in 4LO, the actuator motor did nothing. So I turn the switch back to 4HI, and I still hear nothing, but the 4LO light starts blinking again, but never goes off. So I drive a little to make sure it's in 4HI and it is, so I keep cycling the switch to see if I can get anywhere. It's like the computer thinks the truck is in 4LO, but it's not! Well, I drive home slowish, just to make sure it doesn't jump into 4LO, and it doesn't.

When I got home, I got underneath the truck while my wife was in the driver's seat and had her turn the switch to see if I could hear anything going on, but nothing. I could hear a faint beep when she put it into 4HI, but the actuator wasn't doing anything. I took a rubber mallet to it, I loosened the bolts so it would come out about 1/8" or so and hit it some more. It wasn't budging at all. I checked the connections and everything looks good, but I haven't put a meter on them yet.

I've searched the internet for this specific problem, but I haven't seen it. I've seen where it won't go into 4LO at all, or where it gets stuck in 4LO, but I've never seen where it's in 4HI, but the computer thinks it's in 4LO.

I'm hoping it's just a bad wire, or a blown fuse, or even the 4WD module. If it is the actuator, I can't see how! I cycle 4LO and the CDL at least 3-4 times a month if not more, and it's never given me a bit of a problem. I figured it would take a little longer to lock in, or something to that nature if it was going bad.

So, my question is: Has anyone else experienced this? If so, any pointers on how to go about fixing it? Any way to get the computer to see it's in 4HI so I can actually drive it?!

Also, does anyone have a wiring schematic for the 4WD system? Does the switch tell the 4WD module to tell the actuator to go from 4HI to 4LO and vice versa, or does the switch tell the actuator then the actuator tell the 4WD module to tell the computer where it's at?

Thanks to anyone that reads this whole post!!!:thanks:
 
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I'm not sure what the sequence is either. I assume, to go from 2HI to 4HI, the front diff actuator engaged first which then prompted the transfer case actuator to engage. And vise versa to disengage.

This is of course based strictly on a mechanical drive train perspective. I would think the 4WD system would want to engage the weakest link first (ie; front diff shaft splined hub), then engage the transfer case.
 
scw1991 said:
I'm not sure what the sequence is either. I assume, to go from 2HI to 4HI, the front diff actuator engaged first which then prompted the transfer case actuator to engage. And vise versa to disengage.

This is of course based strictly on a mechanical drive train perspective. I would think the 4WD system would want to engage the weakest link first (ie; front diff shaft splined hub), then engage the transfer case.
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I have the V8, so it's always in 4WD, so I'm assuming the transfer case would be 1st in the sequence?
 
sorry, I should have recognized you have the V8.

So you can still engage 4HI to 4LO and vise versa with no problem? Also the CDL with no problem.

I'm wondering if your CDL never disengaged which may cause the indicator lamp to show 4LO even though it's not.

I've downloaded the service manual download link and under VF4BM or VF4AM there is a complete electrical diagnostics section.
 
Call me crazy, but also from a mechanical perspective. If . . .IF you truly are switching it in at least once a week maybe its premature wear somewhere in the system? I know it may sound a little short sighted seeing how these vehicles are built, but maybe the constant change for short distance could have caused the issue. Sorry and hope you get it figured out, but for me I usually just switch it once a month and maybe drive10-20 miles on it and kick it in f4Lo for about a mile or so then back to 2wd.
 
scw1991 said:
sorry, I should have recognized you have the V8.

So you can still engage 4HI to 4LO and vise versa with no problem? Also the CDL with no problem.

I'm wondering if your CDL never disengaged which may cause the indicator lamp to show 4LO even though it's not.

I've downloaded the service manual download link and under VF4BM or VF4AM there is a complete electrical diagnostics section.
Click to expand...

No...As of right now, I cannot truly engage 4LO, but the computer thinks it's still in 4LO. It's in 4HI now, but like I said, the computer still thinks it's in 4LO
 
wadle5 said:
Call me crazy, but also from a mechanical perspective. If . . .IF you truly are switching it in at least once a week maybe its premature wear somewhere in the system? I know it may sound a little short sighted seeing how these vehicles are built, but maybe the constant change for short distance could have caused the issue. Sorry and hope you get it figured out, but for me I usually just switch it once a month and maybe drive10-20 miles on it and kick it in f4Lo for about a mile or so then back to 2wd.
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Ha! I hope I didn't "over use" the 4LO! I would hope that wouldn't be a problem, but who knows!
 
cpark_12 said:
Ha! I hope I didn't "over use" the 4LO! I would hope that wouldn't be a problem, but who knows!
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Since your truck is almost 13 years old now, nothing works forever. It could possibly be a bad actuator.

I have seen pictures of moisture getting into the small actuator gears and gumming up the electrical contact leads. If you drive in a lot of mud that is my guess.
 
Thanks for clarifying. The actuator motor shaft has a worm gear that turns a plastic spur gear (which in turn is coupled to other plastic gears that move the shift rod back/forth). This spur gear has a set of electrical contacts on the face of the gear. As the gear rotates, these contacts will complete the circuit with another set of stationary contacts.

It is possible to "trick" the 4WD control module if in fact any of the gears are stripped. The actuator motor will still turn the gear to complete the circuit (which would show 4LO on your dash) but if any of the other gears are stripped, then this would inhibit the shift rod from moving back/forth preventing actual engagement of 4LO.

I'm by no means saying this is the case, and sure hope not, but it is feasible.
 
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This doesn't solve your problem, but it gives you a place to start.

There is a breather hose nipple on top of the actuator housing. Check to see if the hose is there. If its not, you might have water ingress into the actuator thats messing with the circuitry.

I have a V8 AWD and i'm 90% positive i've got all kinds of crud in my actuator cause the hose fell off and I didn't know it needed one etc etc.

And a quick story, i'm on my way home from the offroad park, doing 80, and the 4Lo light kicks on for about a minute, then goes back off. I'm like "no truck... you're not doing 80 in 4Lo."
 
swapmeet said:
This doesn't solve your problem, but it gives you a place to start.

There is a breather hose nipple on top of the actuator housing. Check to see if the hose is there. If its not, you might have water ingress into the actuator thats messing with the circuitry.

I have a V8 AWD and i'm 90% positive i've got all kinds of crud in my actuator cause the hose fell off and I didn't know it needed one etc etc.

And a quick story, i'm on my way home from the offroad park, doing 80, and the 4Lo light kicks on for about a minute, then goes back off. I'm like "no truck... you're not doing 80 in 4Lo."
Click to expand...

I'll definitely check that out. Water would definitely make sense if that hose isn't there. Ugh...I've been looking for new actuators just in case.
 
Okay, I finally have a CEL. I hooked the scanner up to it and it read a P1782 code. I searched it and for a 2003 4Runner it shows a "T/F L4 Range Position Switch Performance". I'll dive more into that tomorrow.
[MENTION=66389]BlackWorksInc[/MENTION]

Sorry, but you're the only one I've seen on here that is a Toyota tech. Have you seen this CEL? If so, what did it end up being? Thanks.
 
cpark_12 said:
Okay, I finally have a CEL. I hooked the scanner up to it and it read a P1782 code. I searched it and for a 2003 4Runner it shows a "T/F L4 Range Position Switch Performance". I'll dive more into that tomorrow.
[MENTION=66389]BlackWorksInc[/MENTION]

Sorry, but you're the only one I've seen on here that is a Toyota tech. Have you seen this CEL? If so, what did it end up being? Thanks.
Click to expand...

Hmm, the FSM is saying that the issue is the 4WD Module, the ECM, the communication line between them, and/or any of the above 3. I don't quite trust that though because I doubt the issue is one of the modules or the communication lines (unless you've been playing with the wiring near the glovebox area and/or installing something near there and had the 4WD module unplugged while cycling the key.)

What you're going to most likely want to do after going through the trouble chart in the FSM for the P1782 is to verify that the position switches INSIDE (non-serviceable, it's part of the unit) the actuator are reporting correctly. There should be a section somewhere in the FSM if I remember right that shows a chart on where each switch is supposed to be at a given gear selection, you can then combine that with the pinouts on the EWD to determine what voltages you are expecting to see at the 4WD module.
 
So...just a little update. My brother I started checking the switch, 4wd module, and the actuator this afternoon. The switch and module checked out, so of course, it's the actuator. I was in the truck turning the 4HI/4LO switch and he was underneath with the plug that goes to the actuator checking which pin was lo and hi. We figured that out and drew up a diagram to let us visualize what was going on. He plugged it back in the actuator and we both heard it make a noise. This was a great sound! I got in the truck and the 4LO light was off!

So, I drive it down the road and no codes were thrown! As of now, it's working fine. I haven't been brave enough to switch back to 4LO...maybe one day I will!
 
cpark_12 said:
So...just a little update. My brother I started checking the switch, 4wd module, and the actuator this afternoon. The switch and module checked out, so of course, it's the actuator. I was in the truck turning the 4HI/4LO switch and he was underneath with the plug that goes to the actuator checking which pin was lo and hi. We figured that out and drew up a diagram to let us visualize what was going on. He plugged it back in the actuator and we both heard it make a noise. This was a great sound! I got in the truck and the 4LO light was off!

So, I drive it down the road and no codes were thrown! As of now, it's working fine. I haven't been brave enough to switch back to 4LO...maybe one day I will!
Click to expand...


Post up pics of that diagram...
 
Glad it worked out in the end, I could have sworn I made a thread and posted those exact Toyota Training overviews a long while ago... But those are the same thing I reference when we have 4WD issues similar to yours.
 
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