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Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 13066
Experience:  Toyota Master Diagnostic
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1998 toyota tacoma 4x4: the 4 wheel drive..selector switch..shifter

Customer Question

i have a 1998 toyota tacoma 4x4 and theXXXXXwont engage. it has the 2-4 selector switch on shifter and i push it and no light and it doesnt engage. i checked the fuse in dash and is ok.where do i look now?
Submitted: 3 years ago.
Category: Toyota
Expert:  Skyvisions replied 3 years ago.

Thank you for choosing JustAnswer and allowing me to help you resolve your Toyota questions!

 

Do any of the four-wheel drive indicator lights illuminate or any warning light come on when you tried to engage the four-wheel drive and it does not work? When was last time you had the four-wheel drive engaged? Do you have a manual lever to engage high and low?

Skyvisions

Customer: replied 3 years ago.
truck has been sitting for a couple years, but it didnt work when he parked it. yes it has a manual lever with theXXXXXswitch made in it. i have checked the 2 wires going into the switch (a solid red wire and a white wire with black stripe) and neither is hot with or without key on. no indicator lights
Expert:  Skyvisions replied 3 years ago.
The red wire should have voltage on it. This is the signal input wire from the computer when you turn the switch on it ground this signal wire. Typically it will be either 5 V 10 V or 12 V. There is a 20 amp 4WD fuse do you have 12 V across this fuse and the 10 amp gauge fuse? These fuses are both in the same fuse box. Are you getting any warning lights on for engagement or not engagement of the four-wheel drive?

Skyvisions
Customer: replied 3 years ago.
i only saw 1 fuse in the box that saidXXXXXbut i checked all fuses in the box and all had 12 volts, i am getting no warning lights for neither engagement or not
Expert:  Skyvisions replied 3 years ago.

Unfortunately there's no easy way to test the systems. You need to use a voltmeter and have a pin out chart of all of the four-wheel drive computer inputs and test all of the electrical inputs and ground circuits. If all the power inputs and grounds test good then it's a matter of checking all of the switches like the one in the lever and at the transfer case and front actuator assembly in the front differential. My concern is that there is no power to the red wire to the switch on the lever. This should have voltage on it.

Skyvisions

Customer: replied 3 years ago.
could it possibly be the computer. i also found another box under drivers side kick panel labled 4x4 computer control what is this
Expert:  Skyvisions replied 3 years ago.
That component is the four-wheel drive control computer. There is also a four-wheel drive computer in the center console below the ashtray area. Depending on which model you have will determine which wiring system and computer system you are using. If you're seriously considering diagnosing this yourself and are handy with a voltmeter if you go to www.techinfo.Toyota.com for $15 you can download all of the Toyota factory wiring diagrams and diagnostic step procedures in PDF format. Cannot post them here because it's copyrighted information. But I can guide you through some different steps if you think you can tackle this. If there is any water intrusion due to the windshield leak or this truck has been underwater this could be part of the problem in that control computer. Normally whenever the four-wheel drive will not engage there usually is a warning light in the instrument panel indicating that the command input to engage the four-wheel drive was received but was not act upon. Under normal circumstances the four-wheel drive computers rarely fail.

Skyvisions
Customer: replied 3 years ago.
so this is the one i need to test from and not the main computer behind the dash
Expert:  Skyvisions replied 3 years ago.
If you can post your vehicle identification number I can see if you're system employs both of these computers or just one.

Skyvisions
Customer: replied 3 years ago.
4TAWN74N3WZ039174, its funny this truck is power everything and it all works except this. it has rear differential lock and it works fine also.
Expert:  Skyvisions replied 3 years ago.
You have both. The one in the left kick panel is the basic controller or driver for the rear differential control lock. The brains of the whole operation is the four-wheel drive ECU located in the center console area.

Skyvisions
Customer: replied 3 years ago.
theres the main computer behind the dash pocket, one behind the left kick panel, a air bag computer in the center console and looks to be something like a box mounted under the airbag computer, which one is the brains to the 4x4
Expert:  Skyvisions replied 3 years ago.

The connector is a 16 pin connector and looks at following. Is located right near the airbag computer but I can't find a specific diagram that shows a good location. The computer number and description should be on the top of the computer itself.

 

graphic

Customer: replied 3 years ago.
where is the ADD indicator switch located at and what does it do, and also i unhooked and checked the red wire at theXXXXXswitch and checked with a volt meter and it shows 11.40 volts
Expert:  Skyvisions replied 3 years ago.
The ADD indicator switch is on the differential housing. There is a servo which is operated off the vacuum mounted to the front differential. When the vacuum switching valves are commanded to apply vacuum to the servo mechanism it slides the front differential shift collar into place engaging the front differential. This in turn activates the switch to tell the computer that the front differential is engaged and allows the transfer case to continue the four-wheel drive engagement. I have seen these vacuum hoses become damaged or the vacuum switching valves go bad. You can apply vacuum manually to this diaphragm/actuator on the differential and manually engage the unit. There also couple of four-wheel drive indicator switches on the transfer case and transmission itself.

Skyvisions
Customer: replied 3 years ago.
i found an indicator switch on the motor on the transfer case and it has volotage on the red and white striped wire, i unplugged the wires to the motor and none of them has any voltage, do any of these suppost to have volts , or does power come to the motor later on through the engagement process. also still no indicator lights on in dash
Expert:  Skyvisions replied 3 years ago.
The red wire with a white tracer should have power. The blue wire in the white wire at the actuator is what drives the electric motor to move the selector shaft. If you were to apply 12 V and ground to either one of these two wires and then reverse the polarity it should make the motor in the actuator run. None of these actions will take place until the ADD switch is closed. These systems are very difficult to diagnose because they're so much stuff that has to happen in a certain sequence. You need to make sure the vacuum switching valves are functioning and you can apply vacuum to the vacuum diaphragm actuator on the front differential and see if it is engaging and disengaging. Once this is engaged this may allow the transfer case to move and engage the transfer case and turn the four-wheel drive light on.

Skyvisions
Customer: replied 3 years ago.

i tried putting 12v to the blue wire and ground to the white wire and i could hear the motor click just barely then i reversed and grounded the blue and 12v to white and same thing, just a slight click like it wanted to but couldn't. am i doing this right or not, i dont understand what your saying about changing the polarity. we put vaccum to the actuator on the front diff. and it seems to be working, also both vaccum switching valves is working. i can take the wire loose from the ADD and ground one side of it and theXXXXXwill come on so i know the light works now. seems like all the wires are good just maybe one of the switches or the motor is bad , ANY ADVICE WILL BE MUCH APPRECIATED.

Expert:  Skyvisions replied 3 years ago.
You are testing and checking the actuator correctly by reversing the polarity that is exactly what I mean changing the ground and power supply to the blue and white wire. This basically activates the drive motor to shift into four-wheel drive. When these mechanisms don't get used for long periods of time they get stuck. More than likely what you're going to find is the actuator is not functioning properly. Sometimes if you use a rubber mallet and tap on the transfer case or actuator while trying to apply power and grounds back-and-forth it can break them loose. I would apply vacuum and engage the front differential and make sure the switch is working so the light is coming on so that if you can get the actuator on the transfer case to move you should be able to get it into four-wheel drive.

Skyvisions
Customer: replied 3 years ago.

can i take the motor off the back of the transfer case by taking the 3 bolts out and pulling it off or does it consist of more. thats what i am thinking is wrong is the motor is stuck.

Expert:  Skyvisions replied 3 years ago.
That would seem to make the most sense and the easiest solution. However do not take these bolts out and try and remove the actuator. The transfer case has to be removed from the transmission and disassembled the Rod that goes in the back of the transfer case is held on with clips. If you try to remove the actuator it will damage the actuator or these clips inside the transfer case. :-(

Skyvisions
Customer: replied 3 years ago.
well, i got the motor to break free and it works fine now, and i can manually get it to go intoXXXXX and theXXXXXlight on, but it still wont do nothing by the 2-4 selector switch. the ADD selector valves seem to be working properly also, i dont understand why i cannot get any power to the 2-4 motor or any of the wires on the motor. i also can manually put vaccum to the front diff. actuator and make it engage. i checked the ADD indicator switch wires and both have 12v, is there any way to test these indicator switches or maybe crossing over the wires and bypassing the switches to test the system. as you can guess im just about getting discouraged as is the guy who owns the truck!
Expert:  Skyvisions replied 3 years ago.
Honestly there are a lot of different pin out voltages that you can do but to try and go over them with you in this type of format is probably unrealistic. If you want to continue to try and tackle this project and get it to work exactly like it's supposed to your best bet is to go to the website I listed above and here www.techinfo.Toyota.com these are the Toyota factory troubleshooting manuals and guides. Once you search for the four-wheel drive diagnostic troubleshooting sections it will give you the information that you need and the wiring diagrams. You appear to be reasonably talented and should be able to walk through these voltage tests and checks without any trouble. It's just very time-consuming and tedious. Everything in the system has to happen at the right sequence in order for the system to work correctly. Unfortunately there is no magic answer for these systems when they are screwed up.

Skyvisions

Skyvisions
Customer: replied 3 years ago.
since we couldnt fix theXXXXXhow about another question before i pay? i have a 95 toyota tacoma 4x4, it has headlights on dim but no bright lights, the high beam indicator works and is on but no bright lights, both bulbs is new and also when i pull back on the dimmer switch the bright lights will come on ( with the indicator on also), what you think?
Expert:  Skyvisions replied 3 years ago.

I don't mind working through another problem but the information that I gave you was invaluable. To pay someone for the diagnostic information I provided to you would've cost you several hundred dollars. To come to a total resolution given the type of format were working in with your particular problem is probably unrealistic. Let your conscience be your guide.

 

This being said if you check the wire harness that goes up to the combination switch you will find a red wire with the yellow tracer it is pin number 12. This wire should have 12 V when the headlight relay is turned on either in the low or high beam position. When you push the high beam switch or lever to the high beam position this red wire with the yellow tracer should go to 0 V if it does not the switch contact for the high beam position in the switch is bad. If you ground this red wire with the yellow tracer with a jumper wire it should turn the high beams on.

Skyvisions

Customer: replied 3 years ago.
i didnt mean to upset you, i appreciate all the info you gave me and i apollogize if i came across the wrong way, that being said i wanted to let you know the truck with theXXXXXissue is my brother in laws and he was driving it this evening and reached over and pushed the 2-4 selector button and guess what, it worked, and seems to work well but the motor on the transfer case sounds pretty rough. i think it being stuck was the problem the entire time
Expert:  Skyvisions replied 3 years ago.
No worries, not upset it's just that you would be shocked as to the number of times my talent in time get taken advantage of. Sometimes people don't understand that there are certain limitations to the service and I by no means provide for answers. I am the foremost or shall I say top Toyota guy on here. I believe in providing quality responsible answers or at least guide people in the right direction so that they can resolve their issues and save some money. As far as the actuator on the truck the age and lack of use is probably what is going to end up killing it completely eventually. Sometimes I have seen them get resurrected, time will tell. If it is working and you can make you go in and out I would work the actuator as much as possible to keep it freed up. As far as your the issue with the high beams check that wire there are couple other things but that one voltage test will tell a lot. Get back to me if you need any other assistance.

Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 13066
Experience: Toyota Master Diagnostic
Skyvisions and 10 other Toyota Specialists are ready to help you
Customer: replied 3 years ago.
i checked the red wire with yellow tracer and it has 12v and when i push the high beam lever it still has 12v, do you mean the headlight switch itself is bad or do i have to change the whole combination switch
Expert:  Skyvisions replied 3 years ago.
This red wire with the yellow tracer goes up through the high beam contacts in the switch. You can trace the wire up to the switch make sure that it has 12 V all the way to the switch contact. If you ground this wire it should activate the high beams. The voltage goes to the contact of the switch back down the white wire with a black tracer and to ground. I believe you can replace just the headlight switch portion of the combination switch. You would need to contact your local dealer to verify that.

Skyvisions

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