4x4 troubleshooting... (4hi light blinks, 4lo will not engage) (1 Viewer)

[gman86]

hey guys,

My 2nd generation 2005 toyota tacoma's (auto trans, 6 cylinder) 4x4 system has decided to act up this season... Hoping any of you guys with vast knowledge n wisdom could save me from spending $105 at the dealership for a diagnosis.


PROBLEM- when i select 4hi the vehicle light on the dash blinks (meaning the system has not entered 4x4). However, I have CONFIRMED that it is in 4hi because i jacked the entire vehicle off the ground and all wheels are recieving power. Also, you can hear the transfer case and the front axle ADD actuating to switch vehicle into 4hi when selecting 4hi.

Furthermore, since the 4x4 light blinks continuously (which is saying the vehicle is not engaged in 4hi, eventhough it really is) it will not allow me to go to 4Lo since this would not be the correct sequence im guessing (the vehicle needs to confirm its in 4hi before allowing itself to go in to 4Lo...)

Also, in order for me to get the vehicle out of 4hi I have to turn the truck off and put it in 2 hi, and than turn the vehicle back on and only than will it disengage. It is the only way to get the vehicle out of 4hi once it is engaged.



MY TROUBLESHOOTING- I thought maybe this problem was related to one of the "2 transfer case indicator switches" located on the transfer case that was not relaying back to the truck that the truck really was in fact in 4hi. However, I tested each of these switches and they show no resistance (appear to be working properly)...

Was hoping any of you had some advice or have dealt with a similar problem? Could it be the transfer case motor not actuating all the way and therefore not be 'truly' locked in 4hi?

Thanks for your help n time!!

 

[Josie'sLandCruiser]

Hi All:

Have you tried the late model Tacoma section on the TTORA forum?

www.ttora.com

I have experienced some of the same issues with my 2007 V-6 with the six-speed. It is annoying, no doubt!

I just flipped the 4wd selector knob back and forth a few times and it finally cooperated.

Good luck!

Alan

 

[Mr Chuck Norris]

Since you have confirmed that it does engage in 4-Hi, then it sounds like it's definitely an electrical issue. You're right to look at the switches. If they are normally open (no resistance), perhaps try jumpering the 4wd indicator switch to see if it is not working.

 

[gman86]

Sorry im not familiar with this term but By jumpering you mean somehow bypassing the switch? How do you go about doing this?

 

[Mr Chuck Norris]

Sorry im not familiar with this term but By jumpering you mean somehow bypassing the switch? How do you go about doing this?

If the switch on the t-case is "normally open", meaning it has no continuity when it is not activated and full continuity when activated, then you can "jumper" it by connecting the two wires that go to the switch. This makes the system think that the switch is reading an activated signal.

I don't know off the top of my head if it is a normally open switch though.

 

[ToyotaDon]

The sequence that the 4WD ECU goes through is like this: Actuate 4HI--light blinks and ECU waits until 4HI indicator switch closes. Actuate ADD--light still blinking until ADD indicator switch closes, then turns on solid.

It sounds like you need to check the ADD indicator switch on the front axle.

 

[gman86]

If the switch on the t-case is "normally open", meaning it has no continuity when it is not activated and full continuity when activated, then you can "jumper" it by connecting the two wires that go to the switch. This makes the system think that the switch is reading an activated signal.

I don't know off the top of my head if it is a normally open switch though.

Oh Yea i've already tried this. I was hoping thats what it would be... I get a continous light on both the 4hi and 4lo light when i jumpered or bypassed the switch indicator.

I need to call the service center to find out exactly what that indicator switch is relaying to the system. There is 2 switch indicators on the transfer case...

 

[gman86]

The sequence that the 4WD ECU goes through is like this: Actuate 4HI--light blinks and ECU waits until 4HI indicator switch closes. Actuate ADD--light still blinking until ADD indicator switch closes, then turns on solid.

It sounds like you need to check the ADD indicator switch on the front axle.

Do you know where the switch indicator is for the ADD? Is it encased inside the ADD?

 

[ToyotaDon]

Do you know where the switch indicator is for the ADD? Is it encased inside the ADD?

That's what I get for not checking before typing. Yes, the switch is housed inside the ADD actuator. You can check if the Light Green/Black wire is grounded when the ADD is engaged.



Just so you know, Toyota did issue a Technical Service Bulletin for known issues with the ADD Actuator on '05-'12 models. That's not to say you have to replace it; there may be repair options if you're willing to tear into it.

 

[gman86]

Awesome thank you!

 

[gman86]

That's what I get for not checking before typing. Yes, the switch is housed inside the ADD actuator. You can check if the Light Green/Black wire is grounded when the ADD is engaged.

View attachment 716847

Just so you know, Toyota did issue a Technical Service Bulletin for known issues with the ADD Actuator on '05-'12 models. That's not to say you have to replace it; there may be repair options if you're willing to tear into it.

Hey ToyotaDon,

My brother brought over his ohmeter (he's an electrician), and referencing the diagram you provided we tested for no resistance on the black/green wire (ADD) and completing the circuit through what he believed to be the power wire (white/black on far right)? Don't quote me entirely on this as i am in no way an expert on electrical

Anyhow with the four wheel drive engaged in 4hi we were getting significant resistance while testing the ADD wire. There should not be any resistance in that circuit when the ADD (4hi) is engaged correct? Does this then tell me that the actuactor isn't quite making contact; hence the reason for the 4hi light not engaging?

Im thinking my next step is to open up the ADD and try cleaning the actuator contacts. If that doesn't do it i may take it toyota for a diagnostic because i dont want to just replace the ADD if it is in fact something else.

 

[gman86]

That's what I get for not checking before typing. Yes, the switch is housed inside the ADD actuator. You can check if the Light Green/Black wire is grounded when the ADD is engaged.

View attachment 716847

Just so you know, Toyota did issue a Technical Service Bulletin for known issues with the ADD Actuator on '05-'12 models. That's not to say you have to replace it; there may be repair options if you're willing to tear into it.

Also what is that limit switch on that diagram with the pink/blue and teal green wire?

 

[ToyotaDon]

Hey ToyotaDon,

My brother brought over his ohmeter (he's an electrician), and referencing the diagram you provided we tested for no resistance on the black/green wire (ADD) and completing the circuit through what he believed to be the power wire (white/black on far right)? Don't quote me entirely on this as i am in no way an expert on electrical

Anyhow with the four wheel drive engaged in 4hi we were getting significant resistance while testing the ADD wire. There should not be any resistance in that circuit when the ADD (4hi) is engaged correct? Does this then tell me that the actuactor isn't quite making contact; hence the reason for the 4hi light not engaging?

Im thinking my next step is to open up the ADD and try cleaning the actuator contacts. If that doesn't do it i may take it toyota for a diagnostic because i dont want to just replace the ADD if it is in fact something else.

LOL, an electrician would see a white/black wire and think it's power, but it is in fact a ground wire. He is correct in reading that the switch should complete the circuit with very little resistance when the ADD is engaged. You said before that it is engaging, but I've seen where all the wheels will spin with the truck in the air, then as soon as there's some resistance, they will stop. I would recommend engaging 4HI, turning the engine off, then lifting the truck and making sure the ADD is fully engaged by turning the front driveshaft and holding the front wheels. Either way, you will be replacing or repairing the ADD Actuator, hopefully the latter.

Also what is that limit switch on that diagram with the pink/blue and teal green wire?

The limit switch also tells the 4WD ECU what position the actuator is in. It's not what turns the light on or off, but it tells the ECU whether to keep powering the motor or turn it off.

If you take the actuator apart, be very careful about parts falling out or things getting out of alignment. If you've messed with it and the dealership knows it, they will probably not try to fix it, but just recommend replacement. (They may not try to fix it anyway, that's up to us innovators out in the real world.)

 

[gman86]

haha whoops... see the "gnd" next to it now. suddenly it all makes sense... lol

Well a little good news is that the light is now working. it engages in 4hi and 4lo. it warmed up out here last week so i washed the truck including the underbody (wash the salt away) and suddenly the 4hi n 4lo works with the light staying illuminated. not sure if its cuz of the warm weather or what... or water that got in the part somehow?

Anyways, the 4hi has always worked properly eventhough the light blinked. I know this because i was driving thru deep snow with all 4 wheels pulling. I'm assuming the actuator contactors were not closing all the way to let the vehicle know it was locked, and therefore not let me go into 4lo.

For whatever reason its making contact now either thru constant switching of the 4x4 over the past weeks or because of water or eectrical contact cleaner i sprayed in the actuator and maybe it finally settled? either way im sure i will end up replacing the ADD in the near future...

also, i should actively actuate the 4x4 throughout the whole year. i have a bad habit of only using it when winter time comes around and that probably doesnt bode well for smooth operation.

 

[ToyotaDon]

Glad it's working now. Those actuators technically cannot be rebuilt, but anything is possible if you're trying to save money. Sometimes all that's needed is a little disassembly, cleaning, greasing, and reassembly.

 

[Josie'sLandCruiser]

Hi All:

ToyotaDon, would you have a link to this TSB? Or, do you know what the "fix" was for the problem?

Thanks!

Alan

Just so you know, Toyota did issue a Technical Service Bulletin for known issues with the ADD Actuator on '05-'12 models. That's not to say you have to replace it; there may be repair options if you're willing to tear into it.

 

[ToyotaDon]

I don't have the TSB in a public format, but its number is: T-SB-0066-12

The part that it calls for is the A.D.D Actuator part no. 41400-35032. It falls under the 60 month, 60,000 mile Powertrain warranty.

 

[fedupdon]

have a o5 tacoma that will not shift in to 4 high but will go in ti 4 lo .had the transfer case actuator and the front actuator replaced still n 4 hi do not understand as i was told that it had to be in 4 hi before it could go in to 4 lo. is there a adjustment or a way to set the timing of the actuator motor