KauaiYota, welcome to Toyota Nation! Sorry you are having trouble with your 4WD. Maybe you can glean some information here.

Also do you have a rear locking diff.?

HOW IT WORKS
This is how the 4WD system works. Located above the glove compartment (got to remove) is the 4WD ECU. It could be bad but I have yet to read of one that has been replaced. The 4WD ECU takes inputs and generates outputs as follows:

INPUTS----------------> 4WD ECU
- Rotary 4WD Switch on Dash
- ADD Limit Switch in Front Differential Actuator (tells ECU if front diff. is engaged)
- 4WD Detection (Limit) Switch in the Transfer Case Actuator located on left side of Transfer Case (feeds back to the ECU the current shift position H2 or H4)
- L4 Detection Switch in the Transfer Case Actuator on the left side of Transfer Case (tells ECU that 4Lo is engaged)
- Rear Differential Lock Limit Switch Located in the Rear Diff. Actuator

OUTPUTS from 4WD ECU----------------->
- 4WD Light on Dash
- 4lo Light on Dash
- Servo Motor in Front ADD Actuator
- Servo Motor in Transfer Case Actuator
- 4WD Detection (Limit) Switch in Transfer Case Actuator (feeds back current shift position H2 or H4.

When the rotary 4WD switch is turned from 2Hi to 4Hi the 4WD ECU commands two servo motors to be driven: the motor in the front diff. ADD and the motor in the Transfer Case Actuator. The ADD motor locks both sides of the front differential, and Transfer Case motor moves a shift fork rod to engage the front drive shaft .

Switches in both these actuators feed back to the 4WD ECU that both the front ADD is engaged and the front drive shaft from the Transfer Case is engaged. Also, an additional switch in the Transfer Case Actuator reports to the ECU that 4Lo is engaged when it is selected.

At this point the job of the front ADD is done. One more turn of the 4WD switch on the dash then moves a shift fork rod in the Transfer Case again to engage the lower gear set -- 4Lo, a signal is sent to the 4WD ECU and the 4Lo light is turned on.

POSSIBLE PROBLEM AREAS
1. Check to see that all body grounds are secure and have good contact, not corroded. Specifically, the rear side of cylinder block (right side for V-6), left kick panel, instrument panel brace (RH), right kick panel.
2. 4WD fuse. 20 amp located in the lower dash fuse box.
3. Broken wires, loose or corroded terminals at connectors.
4. Fuse, relay block, engine compartment left, #2, 50 amp fuse.
5. 4WD rotary switch.
6. Problem with motor and/or limit switch in front ADD Actuator.
7. Sticking shift rod in Transfer Case Actuator. Remove cover and see if gummed up.
8. Problem with 4WD detection switch in Transfer Case Actuator. Remove switch and test.
9. Problem with 4Lo detection switch in Transfer Case Actuator. Remove switch and test.
10. 4WD ECU.

TESTING CONNECTORS
Individual wires and combinations to all the components have various test specifications and you would need the factory manual and a diagram.

As far as simple testing of voltage to the servo motor, the connector of the front ADD Actuator includes a red wire (terminal 1) and a black wire/white tracer (terminal 2). When the ADD servo motor is being driven to lock the differential (4WD switch turned 2H-->4H) there should be +12v measured at the red wire (terminal 1) with the black wire/white tracer (-) (terminal 2). The reverse polarity should be measured when the servo motor changes direction (4H-->2H selected) to disengage the ADD.

For the Transfer Case Actuator, there is a lavender wire (terminal 1) and a blue wire (terminal 2) included in the connector. +12v should be measured at the lavender wire (terminal 1) and the green wire (-) (terminal 2) when 2H-->4H is selected. When 4H-->2H is selected the reverse polarity should be measured.

 

KauaiYota, welcome to Toyota Nation! Sorry you are having trouble with your 4WD. Maybe you can glean some information here.

Also do you have a rear locking diff.?

HOW IT WORKS
This is how the 4WD system works. Located above the glove compartment (got to remove) is the 4WD ECU. It could be bad but I have yet to read of one that has been replaced. The 4WD ECU takes inputs and generates outputs as follows:

INPUTS----------------> 4WD ECU

• Rotary 4WD Switch on Dash
• ADD Limit Switch in Front Differential Actuator (tells ECU if front diff. is engaged)
• 4WD Detection (Limit) Switch in the Transfer Case Actuator located on left side of Transfer Case (feeds back to the ECU the current shift position H2 or H4)
• L4 Detection Switch in the Transfer Case Actuator on the left side of Transfer Case (tells ECU that 4Lo is engaged)
• Rear Differential Lock Limit Switch Located in the Rear Diff. Actuator

OUTPUTS from 4WD ECU----------------->

• 4WD Light on Dash
• 4lo Light on Dash
• Servo Motor in Front ADD Actuator
• Servo Motor in Transfer Case Actuator
• 4WD Detection (Limit) Switch in Transfer Case Actuator (feeds back current shift position H2 or H4.

When the rotary 4WD switch is turned from 2Hi to 4Hi the 4WD ECU commands two servo motors to be driven: the motor in the front diff. ADD and the motor in the Transfer Case Actuator. The ADD motor locks both sides of the front differential, and Transfer Case motor moves a shift fork rod to engage the front drive shaft .

Switches in both these actuators feed back to the 4WD ECU that both the front ADD is engaged and the front drive shaft from the Transfer Case is engaged. Also, an additional switch in the Transfer Case Actuator reports to the ECU that 4Lo is engaged when it is selected.

At this point the job of the front ADD is done. One more turn of the 4WD switch on the dash then moves a shift fork rod in the Transfer Case again to engage the lower gear set -- 4Lo, a signal is sent to the 4WD ECU and the 4Lo light is turned on.

POSSIBLE PROBLEM AREAS
1. Check to see that all body grounds are secure and have good contact, not corroded. Specifically, the rear side of cylinder block (right side for V-6), left kick panel, instrument panel brace (RH), right kick panel.
2. 4WD fuse. 20 amp located in the lower dash fuse box.
3. Broken wires, loose or corroded terminals at connectors.
4. Fuse, relay block, engine compartment left, #2, 50 amp fuse.
5. 4WD rotary switch.
6. Problem with motor and/or limit switch in front ADD Actuator.
7. Sticking shift rod in Transfer Case Actuator. Remove cover and see if gummed up.
8. Problem with 4WD detection switch in Transfer Case Actuator. Remove switch and test.
9. Problem with 4Lo detection switch in Transfer Case Actuator. Remove switch and test.
10. 4WD ECU.

TESTING CONNECTORS
Individual wires and combinations to all the components have various test specifications and you would need the factory manual and a diagram.

As far as simple testing of voltage to the servo motor, the connector of the front ADD Actuator includes a red wire (terminal 1) and a black wire/white tracer (terminal 2). When the ADD servo motor is being driven to lock the differential (4WD switch turned 2H-->4H) there should be +12v measured at the red wire (terminal 1) with the black wire/white tracer (-) (terminal 2). The reverse polarity should be measured when the servo motor changes direction (4H-->2H selected) to disengage the ADD.

For the Transfer Case Actuator, there is a lavender wire (terminal 1) and a blue wire (terminal 2) included in the connector. +12v should be measured at the lavender wire (terminal 1) and the green wire (-) (terminal 2) when 2H-->4H is selected. When 4H-->2H is selected the reverse polarity should be measured.

My 4wd question is very odd to me, but really need help with.. 09toco access cab 4.0 automatic.i shift to 4hi pulls like acharm. But try to go into 4low and yes exactly as fixed above says to .I have nothing, as in 4low I ha e movement at all..like it's all in neutral. Again 2hi great 4hi great but 4low nothing at all. Please help.

 

Taco "09, WOW! No idea how you know all this stuff but thank you sooo much. that was exactly the info I was looking for. Im pretty sure I can diagnose now that I have a basic understanding of the the order of things. I Will post once I diagnose and repair. Oh, to answer your question, yes I do have a locking rear diff. C

 

IF the indicator is flashing all the time, could indicate the thing thinks the actuator is in transit, ie both switches made at the same time.

Usually 1 sw made in 2wd, the other in 4hi. While transitioning, both are made, and it flashes. Suspect your reconnect either fouled up the wiper, or the wires.

The switches work via (as shown on the drawing) an arc, there the pivot is at the center of the arc, and the wiper moves along the arc as the motor moves the assembly back and forth. There are two arcs in parallel, and their ends are not even. The 2WD switch starts on the arc, while the 4HI starts off the arc. When the 2WD hits the end of its travel, the switch falls off the arc. The 4Lo says on the arc at the end..

Sorry, don't have colors available to me, but typically 5 wires going into the transfer case, 2 for the motor (similar colors), and 2 plus ground(blk/white) for the switches (again, similar colors)

The 12V for the motor reverses between going into and coming out of 4WD, and is off at either end.

Hope this gets you going, more later when I can see the color chart for the wiring.

 

Thanks for the help, but drawing? What drawing? :headbang:

 

Couple of clarifications, some guessing here, but I believe this is how it goes

Flip switch H2 to H4 (LED flash)
Motor moves transfer case (see below)
Motor moves front diff
LED stop flash

Lets move in short steps, assuming switch works since you swapped it out. Lets first decipher if the transfer case switches. Assuming you have a meter and know how to use it. BTW, switches here are linear, not arcs. Arcs are in diff cases.

All colors etc based on 05-06

Motor on Transfer case is green (G) and light blue (L) wires, should be 12V+ going into 4H, reversed coming out of 4H in to 2H.

Limit switches are Light Blue / Yellow (LY), Light Blue/ Black(LB), and Light blue/ White (LW), with white/black (WB) as the ground.

When you are sitting still, in 2H, with the switch in 2H, no power to motor, and continuity between

LY - WB
LB - WB

When you switch to 4H, the motor pair should see 12V+ (don't know which way) G & L

The motor drives the mechanism, and the limit switch
LY- WB
should go off. This will turn off the motor signal as well. transfer case is in 4H.

Realize now I wrote this all up in another post, will look in the archives to find the rest.

Make sure your transfer case is switching appropriately, then we will tackle the front diff switch from the archives. Link to follow

 

http://www.toyotanation.com/forum/61-2nd-generation-2005/622906-4x4-issue-2.html#post5965329

Poke around here for info on the front diff. Lotta good info in the whole thread, the post I linked is just the controls

http://www.toyotanation.com/forum/61-2nd-generation-2005/622906-4x4-issue.html

 

4X4 Fixed!! So heres how it went. . After the messages from Kauai09' and RTFM, armed with my new knowledge I at least felt like I was ready to do battle with this 4X4 issue. I ALSO WAS able to find a FSM online! I took a page out of that and put it on my ipad and brought it under the truck with me. It told me which terminals on the front diff actuator did what and what the resistances and readings should be. I tested them and they came out within specs. Next it said to apply 12v to pins 1 and 2 and listen to see if the motor moved and so that I could test more resistances from the other pins to see if the position sensors were operational.Since the sensors were my #1 suspicion, I went ahead and did that. I hooked 2 small alligator clip wires up to pin #1 and #2. You've got to be careful not to let them touch or a short could occur and they are very close together. I put a small piece of rubber between them just to make sure they wouldnt touch . I took the other end of these wires and hooked them to a pair of jumper cables that were attatched to the battery. I could hear the actuator doing something. so then, I got another idea. I hooked up the polarity so that it put the ADD in "engaged" mode (the Page of factory service manual that told me all this is right here:

***Links to FSM not allowed***

Go down to the second page (DF-6 at upper left corner) half way down the page it says "inspect differential vacuum actuator assembly" thats what they call the actuator, not sure what vacuum has to do with it but whatever. the picture to the left shows the actuator pins and has them numbered. the chart below, at the bottom of the page, shows what polarity to put pins 1 and 2 to and which polarity setting is "connected" and which one is "disconnected". Anyway, I put it to "connected". Then I thought. I wonder what would happen if I plug the actuator back in and start the truck? will the 4X4 light now stay solid? So I removed my alligator clips and plugged the actuator back in. I got in the truck. Now, I didnt want to further confuse my 4X4 system so before I even turned the key, I put the 4X4 selector in 4hi so everything would be lined up (front actuator in 4Hi, selector switch in 4hi) I started the truck. The 4X4 light came on, and it was solid.. .YEAH!! so then I turned the switch back to 2hi, the light blinked and went out. What?!? now its working? next I put the switch BACK in 4X4 Hi. it went right in! So I tried 4L0. Went right in again. I took it back into 2hi, closed the hood and went to drive around. My grass was wet so I figured i would go into 4 hi so not to tear up the yard. I had the truck in reverse by now and i flipped the switch to 4Hi, blinking.. the dreaded blinking again. I switched it back to 2 hi.. More BLINKING NOOOO. I put the truck in neutral and switched the switch back and forth and after a couple seconds the light turned off. I pulled out on the street and drove about 10mph and switched to 4Hi, blink blink blink... click it goes in again. Anyway, I kept driving around and switching it back and forth, the more I used it the better it got. It now clicks in and out right away. 4lo works every time as well. It kinda sucks when you fix something and dont know the EXACT cause and dont find a failed component, but here are my thoughts. When I originally pulled the ADD to inspect, I have a feeling that it was probably part way stuck already between engaged and disengaged. I pulled it, inspected it, saw nothing and put it in EXACLTY the same way, just as I had found it. when I plugged everything in again the 4X4 ecu was confused and started blinking ALL the time. with the sensors throwing mixed signals Im just guessing that the 4X4ECU wouldnt send the 12v to move the actuator motor and thats why I never got a reading when I originally tested the actuator plug. Seems like Im reaching on that one but the thing I failed to do when I had the actuator out of the truck originally was put 12v to it and watch it move back and forth. If I wouldve done that I could have determined if it was working for sure AND I wouldve seen that when I pulled it, it was in between engaged and disengaged. Again Im just guessing here. If you need help with a 4X4 system not working I STRONGLY suggest that you look at that link I posted above and follow the diagnostic procedures to determine if your add actuator is working or not. If the readings dont come out right, it simply says "replace differential vacuum actuator" what that would say to me is "remove differential actuator and have a look inside. There are some guys on here that solder connections and repair them. Look at this epic 4X4 tacomaaaa!! Ready to drive on the beach!

 

Man, now that I got the 4X4 working, i realized that the Rear locker is inop. I put the truck in 4lo, was at a standstill, and the rear diff light just blinks. What is it with me and blinking lights on my dash! I tried it several ways, rolling slow, nuetral, park reverse. Its just not going in. Back under the truck I go. What you got RTFM? By the way, thank you SOOO much for your help on the 4X4 issue. I beleive that you were basically right about the sensors being confused. Thank you to Taco09' as well.

 

KauaiYota, GOOD JOB!

Hey RTFM, another one fixed. Thanks!:banana2:

Now on to the rear diff. lock.

As far as your rear diff actuator, all these actuators are basically alike and operate in the same way: little 12v motors move a shift fork and limit switch.

I don't know where the notion came from that the hose on them is a vacuum tube (2nd Gen.)....it is actually a vent hose or snorkel if you will for you guys in Hawaii.... It will however take in water to the actuator if the hose is broken or off, so always think water intrusion....

Here are the terminals at the diff. lock actuator's connector to test the motor:
Terminal 2: light green/red tracer
Terminal 3: light green

Unless someone has modded it, the rear diff. lock is supposed to work only in 4Lo.

Here is what the factory electrical wiring diagram manual says:

"Switching diff. lock on when in the L4 position.
When the diff. lock switch is turned ON with the 4WD control switch in the L4 position, this signal is input to the 4WD control ECU (TERMINAL R). Then, the 4WD control ECU drives the diff. lock shift actuator (TERMINAL 2, TERMINAL 3) in the diff. lock shift actuator assembly until the shift fork shaft shifts to the diff. lock position, locking it in the L4 position with the diff. lock."

Again, test for all the basic wiring/terminal faults and check for water intrusion and if the shift fork is sticking and motor bad.

 

Most repairs in a day record?

So today was a good day for this truck! 4X4.. Fixed! Locking Diff.. Fixed.. And just do go for the record I did Mcmixmasters repair of my accessory meter. Worked like a charm.

http://www.toyotanation.com/forum/2314842-post38.html

I would post the FSM link that I used to diagnose the Rear Diff but apparantly thats against the rules. I just went with what I alredy learned on the Front diff. It might be stuck! I jumped the rear Diff and it clicked over. Then I drove it. It was having trouble engaging at first too but it def helped to turn the wheel back and forth while slowly driving (get the rear wheels to turn at a different speed and thus turn the gears in the rear diff to help them line up) Again, once it switched over a few times everything was good. The previous owner told me he never even engaged 4wd and he didnt even know it didnt work till they told him when it was being serviced at the dealership. I think its the usual case of if you dont use it, you lose it. Anyway, if I had the new Antennae part here I would replace that too and just go for 4 fixes in a day.

 

So today was a good day for this truck! 4X4.. Fixed! Locking Diff.. Fixed.. And just do go for the record I did Mcmixmasters repair of my accessory meter. Worked like a charm.

http://www.toyotanation.com/forum/2314842-post38.html

I would post the FSM link that I used to diagnose the Rear Diff but apparantly thats against the rules. I just went with what I alredy learned on the Front diff. It might be stuck! I jumped the rear Diff and it clicked over. Then I drove it. It was having trouble engaging at first too but it def helped to turn the wheel back and forth while slowly driving (get the rear wheels to turn at a different speed and thus turn the gears in the rear diff to help them line up) Again, once it switched over a few times everything was good. The previous owner told me he never even engaged 4wd and he didnt even know it didnt work till they told him when it was being serviced at the dealership. I think its the usual case of if you dont use it, you lose it. Anyway, if I had the new Antennae part here I would replace that too and just go for 4 fixes in a day.

Now that everything is "working", time for the http://www.toyotanation.com/forum/61-2nd-generation-2005/226409-locker-mod-alternative.html

BTW - I've had similar issues, but living in CO, I need 4 wheel drive a lot in the winter, so it gets quite a work out.

 

Woo hoo. Glad to hear it all worked out. Knowledge is wonderful, glad you were able to put all the pieces to make it go.