4wd flashes in 2wd.

[bivey]

Just bought a 4runner and everything was fine. Yesterday went to lunch and came back to work and noticed that the 4wd light was flashing. I didn't notice if it was flashing when I went to lunch. I can never get it to engage in 4wd. This happened once before but I moved the lever without pushing the button or having it in neutral. I drove home like that parked and went out the next day and it was off. Just wondering if anyone has had this problem and how they fixed it. I tried to disconnect the battery to reset the computer but that didn't work. Also when I press the 4wd button, the light goes off for about 10 seconds then starts flashing. It's a 99 limited. Also I hear no clicking from the relay.

 

[Singtoe]

Search my friend.. :juggle:

I just went through this. Everybody's advice so far is flat out wrong. Even the picture they have is wrong. Pushing buttons and shifting to neutral will not fix the problem.

You have an Electronic control system for your AWD/4WD system. You have no vacuum lines or VSV's for your 4runner.

Why does it blink? Because the AWD/4WD Ecu is getting signals that do not correspond to the position of the Actuators.

You have 2 electronic actuators. One in the front diff which engages the passenger axle with the front diff and one in the transfer case. It engages the 4wd and further locks the center diff.


So what is wrong with your 4runner. It is permanently locked in 4wd. With out diagnosising it in person, I would suspect the transfer case actuator. It engaged into 4wd and the actuator can't reverse itself.

Take the actuator cover off the tranfer case. It will be held on with three bolts. Check the race ways inside for corrosion and see if the spindle can turn by hand.

Do not pull the gear out of the transfer case like the picture. It will be hard to put back in correctly.

If everything is clean and the spindle spins smoothly then one of your transfercase switches is bad. Easy to check- remove switch and test with multimeter. These switches look like this and there are 3 of them.

Good luck and God Speed.

You do have Vacuum lines on your truck. In addition to the above, Check your vacuum lines on the drivers inner fender for leaks or disconnections.

 

[bivey]

Thanks ill try that but I have been searching for two days and trying the tricks.

 

[topless87]

Do me a favor and take it to dealer. LOL

 

[bivey]

Maybe

 

[topless87]

I am working on bivey's 4runner. By what all data and toyota dealer repair manuals i checked the switch i am getting continuity through the switch. so next step is move to relay. well where in hek is the ADD relay? Says it is in the passenger side kick panel but can not see it anywhere. I moved on to the front add switch and i do not get any continuity through this so manual says replace. but before i replaced i took my power probe (suped of test light) i put power on the power side of switch and this engaged the 4wd. well now it will not disengage. I replaced the switch as specified but still in same shape. we are at the point of replacing the transfer case. Any better ideas? HELP PLEASE

 

[Singtoe]

I am working on bivey's 4runner. By what all data and toyota dealer repair manuals i checked the switch i am getting continuity through the switch. so next step is move to relay. well where in hek is the ADD relay? Says it is in the passenger side kick panel but can not see it anywhere. I moved on to the front add switch and i do not get any continuity through this so manual says replace. but before i replaced i took my power probe (suped of test light) i put power on the power side of switch and this engaged the 4wd. well now it will not disengage. I replaced the switch as specified but still in same shape. we are at the point of replacing the transfer case. Any better ideas? HELP PLEASE

You have engaged the Front ADD when you tested the power probe to it.

Lets make some assumptions. You have check all the hoses to make sure none of them are cracked and or leaking vacuum.

Check all the connections to make sure they are not corroded or loose.

Check your fuses , to make sure they're not blown.


After all this is done. Check all your switches for continuity. There are 3 on the transfer case and one on the ADD servo on the front diff.

Once all the switches check out, remove the actuator and check the race ways for corrosion. Do not remove the gear from the actuator as it is very hard to realign.

BTW, The add relay is a rectangular box the size of a juice box under the plastic kick panel on the passenger's side.

 

[topless87]

done all of the above. we are at the point of testing the transfer case actuator. problem is that it is cheaper and less time consuming just to replace the t case. 8.8 hours to remove the actuator. its only 350 to get new case. so gonna go that route.thanks for all info

 

[Singtoe]

done all of the above. we are at the point of testing the transfer case actuator. problem is that it is cheaper and less time consuming just to replace the t case. 8.8 hours to remove the actuator. its only 350 to get new case. so gonna go that route.thanks for all info

Just remove the actuator cover and check the contacts. You do not need to remove the actuator from the transfer case.

This would take 10 minutes to check.

 

[topless87]

done that and checked the gear to see if it free spun and did not

 

[Singtoe]

So , what does not spin. The motor or the gear on the actuator?

 

[topless87]

nothing inside the acuator spins. I put the t case in friday and it did not fix it. i put the front add switch in the front and did not fix it. i have checked all vaccum lines and swapped them. the blue actuator under the hood has power and vaccum and the brown one has neither. but i noticed the relay does not click as it does in my 99 when engaging the 4wd.

 

[Singtoe]

Did you check the fuses?

 

[topless87]

that was the very first thing i check. i only found the one and it would not flash if it was blown. im at a lose. i really truely believe its the add relay but can not find it on the passenger side. found a big black box looking thing that says 4wd controler next to the 4wd ecu on the drivers side

 

[Singtoe]

that was the very first thing i check. i only found the one and it would not flash if it was blown. im at a lose. i really truely believe its the add relay but can not find it on the passenger side. found a big black box looking thing that says 4wd controler next to the 4wd ecu on the drivers side

The 4wd ecu is it. The limited had an 4x4 ECU that takes input from the 4x4 button and the j shifter position and controls the actuator on the Transfercase and the ADD valves on the drivers inner fender.

The 4wd controller is for the rear diff lock.

The non limiteds have the relay pack that controls the ADD valves. It reads the engagement switch on the tranfercase and relays power to the appropriate ADD valve. This relay pack is on the passenger side.





So you replaced the tranfer case - I hate to see what you do when a check engine light comes on.


None the less, You have knocked the actuator and the transfer case switches (assumming that the new ones were 100%) out of the equation so that leaves just a few things.

The wiring - from the front diff switch
the front diff switch
the two vsv valves
the hoses and vacuum storage tank
and the ECU. No relays

ADD valve control
When switching between 2WD to 4WD, the VSV is controlled to free or lock the ADD.

At this time, current flows from the 4WD fuse to TERMINAL 12 of the 4WD ECU to TERMINAL 23 to VSV (2WD, Green Wire with red stripe) or flows TERMINAL 10 to VSV (4WD, Light green wire).

 

[TheDurk]

I have read this thread twice and I can't really understand what is going on. Here is a post I have made several times about troubleshooting the ADD circuit (a search would have found it) and I suggest you take a deep breath and go through these steps. At the end, you will know if the fault is in the TC, the VSV's or the front diff. At the moment, you really know very little except what you have changed.

VSV’s/ADD
Don't guess at it, troubleshoot! Start at the twin VSV's (Vacuum Switching Valves) on the driver fender wall. There are two long vacuum hoses that come up from the diff, one goes to each VSV. Check to see that one of the two hose nipples on the VSV’s has vacuum (engine running, 4WD NOT engaged. If no vacuum either side, check the check valve going to the intake manifold and look for loose hoses or a hole in the reservoir. If there is vacuum going to one hose, then put it in 4WD. See if the vacuum switches to the other hose. If it does, and no 4WD, problem is the diff actuator or the line to the diff. If it does not, then just switch the hoses and you should go into 4WD. This confirms diff is okay.

OK, switch them back. Then use a test light to see if electrical signal from the TC also switches sides of the VSV. If it does not, problem is the TC, the switch on the TC, or the TC actuator, or its wiring back to the button (last two for non-J shift only). If it does, but the vacuum does not, the problem is the VSV itself.

I start troubleshooting at the VSV's because you can figure out where the trouble is without having to climb under the truck.

You said you "swapped the hoses", but you didn't tell us what happened when you did. This is very important info.

 

[topless87]

i have vaccum at the storage tank. i have 12.4 volts on power wire of the front add switch. so i was thinking that would rule out the vaccum accuators in the drivers side inner fender. but the brown one has no power. but the blue one does. im at the point of just giving up. i have no hair left.

 

[Singtoe]

Do you have ground at those switches? Switch the the plugs between the vsv's and see what happens. You should hear the ADD lock.

This will verify that the front servo is good.

 

[TheDurk]

i have vaccum at the storage tank. i have 12.4 volts on power wire of the front add switch. so i was thinking that would rule out the vaccum accuators in the drivers side inner fender. but the brown one has no power. but the blue one does. im at the point of just giving up. i have no hair left.

The front ADD switch power wire always has power. The return wire goes to the light which comes on once the front diff engages. It really says nothing about the VSV's. You have to slow down and understand how this thing works:

Driver engages 4wd at button>>4wd is called by the 4wd ecu>>TC actuator engages 4wd>>4wd sending switch on TC (thru 4wd ECU) switches power from brown to blue (or vice-versus, I forget which--the important thing is it switches)>>vacuum switches to other hose>>actuator in front diff engages ADD>>front diff switch (thru 4wd ecu) turns on light.

So you really need to report status of vacuum and power at each of the VSV's when 4wd is engaged and when it is not. They both should change from one to the other. If you can report this info, I can help you. But it does no good to say "the brown one has no power. but the blue one does" unless you tell me that status in both 2wd and 4wd settings.

Give me the info I need and I can help you find the fault.

 

[TheDurk]

Do you have ground at those switches? Switch the the plugs between the vsv's and see what happens. You should hear the ADD lock.

This will verify that the front servo is good.

But if it doesn't click in, the fault could be in the VSV OR in the diff. So I prefer to test the diff by switching hoses--after verifying that one side has vacuum and the other does not. Just remember to switch them back.

I'm not sure if you can always hear it over the engine, which needs to be running to give vacuum. But if you switch hoses while in 2wd, the propeller shaft should go from free-spinning to locked--then you are SURE the front actuator is working.