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Discussion Starter #1
Hi, I have a 06 tacoma 4x4 reg cab, 4cyl, manual trans, and the 4x4 selector is the turn switch type. It will shift into 4hi and the light comes on, but when I switch it into 4low it does not shift into it and the 4low light does not come on (it stays in 4hi). No beeping either. I did as the manual said: come to a stop, put in neutral, depress clutch all the way down, push and slowly switch into 4low from 4hi. I've tried turning the wheel both ways, and moving forward and backward multiple times. I don't see why the 4low light won't come on or even blink. Nothing is showing up on the code reader, and I've checked the fuses and conections on the t-case actuator. I hope it's not the actuator (i've heard they're around $800). I would appreciate any insight.
 

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OP, how frequently do you engage your truck into 4lo? If it is rarely, this problem has become to be known as the use-it-or-lose-it problem and is rather common.

Let's try and rule out the clutch switch. Do you use the clutch cancel switch on the dash to start your truck or do you push the clutch to the floor to start it? I'll have to check the diagram as I am not sure at this point but the same switch may be used for both starting the engine and engagement of 4lo. I have the same truck as yours, different year. I use the clutch cancel switch to start mine but when I do engage it into 4lo I find I have to really plant the clutch hard on the floor in order for it to work.

Also, mine had the same problem as yours when new. When it says to to be stopped, in neutral, and push in the 4lo switch and turn it slowly it means s--l--o--w. Mine did get a bit better with time.

Also, try your steps with the engine off and listen to see what the motor on the transfer case is doing. Do you hear a click from underneath the dash by the glove box when you try to switch it to 4lo?

Finally, there is a thread somewhere that indicated if the front differential actuator was starting to act up it would in turn prevent the 4lo from functioning.

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EDIT: I just looked in the shop manual for this problem and will paraphrase it here:

Problem: Shift From 4hi to 4lo Not Possible

Possible Problem Areas Ranked in the Order of Probability

1. 4WD Rotary Control Switch

2. Wire Harness (lose or corroded connections, bad ground)

3. 4WD ECU control unit. Located under dash just above and to right of glove compartment.
 

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Discussion Starter #3
Hi, thanks for the reply. This truck is new to me so I don't know how much the 4wd was used. When I switch to 4hi it acts normally (with the light on and the dash clicking). I also feel the front wheels engaging. When I switch to 4lo, there's no light at all or clicking under the dash or lower gear engaging. It just stays in 4hi. I haven't used the clutch cancel button to switch to 4wd but I know it does function. I'll try to use it next time.

I tried slowly switching the selector to 4low several times but I can't hear any response from the t-case.

I'll try to switch it with the motor off.

If the diff actuator was messing up why would the 4hi work perfectly? Just wondering.

I'll check the 4wd ECU and the connection to the diff actuator.

Thanks again for the responce!
 

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You misunderstood me. Don't use the clutch cancel switch to try and engage 4lo. It will do nothing. I was merely trying to rule out the main clutch switch on the pedal.

If the 4WD was never or infrequently used by the previous owner, there may lie your answer. Similarly, it could of been abused. Give them a call.

If it were mine I would try to follow the three steps per my edit at the end of Post No. 2 as those are the ones Toyota says are the most likely.

1. That 4WD switch is tops on Toyota's list of probable problems. It is easy to take out and to take apart. There may be a test (continuity-ohms) somewhere. It has a single connector on the back that might reveal a bad crimp. If you are a little more gung-ho you can make some notes and index the back side of the switch, disassemble it and see what the contacts inside look like.

2. I have found a number of poorly crimped wire terminals on my truck. The terminals are machine-crimped at high speed to make the harnesses. Also, being an '06 you could easily have a corroded ground somewhere. Toyota has a "wiggle" test for its wiring harnesses to try and isolate poor crimps. If you can get the glove box out look at the wires where they enter the 4WD ECU. The 'wiggle" test is done by wiggling the wire harness when you are trying to make the 4lo work. Sometimes this makes or breaks a contact momentarily and narrows the search. You can "wiggle" test the other connectors as well.

That whole electronic 4WD system uses feedback mechanisms. A number of people have tried do a 2lo mod without engaging the front actuator. So it apparently plays a role. That front actuator is also known to take in water. So if the previous owner liked doing water crossings or there is a crack in its breather tube.......

Good luck!
 

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OP, I did some further reading on your problem and it does not seem to be uncommon. The posts I located appeared to weigh toward the transfer actuator parts either gumming/gunking up due to lack of use, or contaminants entering the actuator parts, both which prohibit complete 4WD shifts or a locking in place of a shift. There were also some posts related to the front ADD actuator affecting this as well.

I'll post one link here because this guy says it all about the transfer case actuator problem and his repeated cleaning efforts in the first paragraph and went on to get serious about it and much more.... http://www.pirate4x4.com/forum/toyota-tacoma/898689-2005-tacoma-get-fj-cruiser-t-case.html
 

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Not had this problem, working off diagrams, so not sure how true this is:

The wiring harness from the 4WD ECU to the transfer case has 5 wires going through it. Since 4Hi works, might be a partial failure of any of these systems. This assumes a full failure, but read as the 4hi to 4Lo as a free standing system. ie investigate only that half .

Since only 1 motor and 1 motor signal, I suspect when you engage from 2HI to 4Hi, motor runs til you hit the limit switch, then stops. Same from 4Hi to 4Lo. When you go backward, I assume the same, with a reverse voltage signal, and looking for the opposite set of LS to make

Color code Name Terminal at Transfer case (Terminal at ECU)
Green - TM1 Motor T2 (t2)
Lite Blue - TM2 Motor T1 (t1)

Lite Blue - Yellow TL1 Limit Switch T5 (t25)
Lite Blue - Black - TL3 LS T3 (t23)
Lite Blue - White TL2 (yes, out of order) LS T6 (t24)

Plus
White - Black GND Ground t4

If you have someone else in the truck, and crawl under, you should hear some clicks and thunks once the switch is engaged. If not, either the ECU has failed, or the wiring to the motor, or the motor has failed (doubtful since 4Hi works but could be bound up to not get to 4Lo).

When you engage the 4Lo switch, you should get a 12V +/- signal going down to the Motor. Take the connector off near the motor, check for the presence of 12V with a meter. Going out of 4Lo should reverse the voltage of the signal. No 12V here means ECU or wiring bad. Go back to the ECU end of the harness, and repeat the process. If you get 12V here means the ECU is OK, and the wiring is bad.

If you do hear clicks and thunks, could mean the Limit Switch is bad.

The following is a guess, not exactly sure this is how the switch works

with a meter, you should see continuity From Ground to TL# as follows, if the motor is working (if this didn't work, suspect you would get flashing.

2Hi - TL1, TL2,
4Hi - TL2
4Lo - TL2, TL3

Been a previous thread where someone found his rear Diff all full of crap, preventing the motor from moving.

Also been a thread of bad connectors at the diff or transfer case, full of crap, broken wires, etc

Good luck
 

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Discussion Starter #7
hi, thanks for the input.

I kind of know the owner, he worked in the same building I did for
 

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Discussion Starter #8
Sorry for the cut up post.

Anyway, I don't think he did much 4wheeling with it. so I doubt there's trash or water in the system. I could be wrong though. I hope its just a bad switch or something loose like y'all said.

I'll try to look at the wiring soon. I have a full plate this week.

I'm trying to think If I have a voltmeter anywhere. :\
 

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Discussion Starter #10
hey guys,

I'm not 100% sure at this point, but I think its the switch. I pulled it out and noticed that when the selector is in the 2hi position it can move out of that detent spot and rotate slightly more out of position. When it is switched to the 4low side the detent ball in the switch is not able to click in the correct position (the travel of the selector is stopped too soon). On the electrical contact side of the selector, it appears that it needs to rotate a little more to make a good full contact for 4low to work.

I'll see soon if this is the problem. Thanks for the suggestions.
 

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hey guys,

I'm not 100% sure at this point, but I think its the switch.
Well hell. Who'da thought the simplest piece would fail. I didn't even include that in my troubleshooting, since I doubted it would go bad.

Three wires coming out of switch

White - Black - Ground

Gray 2-4

Lite Blue - Low

In 2Hi, the Ground is direct connected to gray

In 4 hi, ground connects through a pair of diodes to both

in 4lo, the ground connects directly to blue
 

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Well hell. Who'da thought the simplest piece would fail. I didn't even include that in my troubleshooting, since I doubted it would go bad.

Three wires coming out of switch

White - Black - Ground

Gray 2-4

Lite Blue - Low

In 2Hi, the Ground is direct connected to gray

In 4 hi, ground connects through a pair of diodes to both

in 4lo, the ground connects directly to blue
I should have said something before because I wondered if it could be the switch based on the fact that there was no flashing 4Lo light.
 

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Discussion Starter #13
It turns out that somebody didn't push and turn the switch to get in 4low. He/she just turned and torqued the @#$%! out of it. I guess some people can't read?

So the bent plastic piece allows too much rotation in the 2hi direction and not enough for the 4low position. :headbang:

4x4 selectors are $40ish online, but I wonder if I can just heat that part and bend it back to shape?

It won't hurt to try. :D
 

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If you decide to buy,
TOYOPARTSMAN is a member here, he is the parts manager at a toyota dealer in Georgia, usually gives TN members % off.
 

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Discussion Starter #15
Hot diggidy dog! It' fixed. I took a lighter and heated the plastic piece, bent it back, and held it till it set. I assembled it and plugged it back in the truck. It worked the first time! I am so glad I joined this forum.

Thanks everybody for the suggestions and links! This is how information on the internet should be.
 

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Cool. Pocket the $40 for the next project.
 

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Same here, my 2006 needs to have the 4 low switch held tight to the right to engage, does it every time, but is not indexed proper if you just drop it in to 4 low position. duh.
 
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