4 wheel drive won't engage
11-01-12, 11:02 AM
#1
Driver School Candidate
Thread Starter
4 wheel drive won't engage
After I push the switch for the 4 wheel drive, the light on the dash blinks but the front differential won't lock in even after driving around the block. Does anyone have a possible solution or fix for this. Thx in advance.
11-01-12, 11:35 AM
#2
RT It would be better if you could get the fault codes posted here and we can take it from there, to know the exact nature of the fault. If you have OBD scanner well and good, otherwise Most auto parts stores ( Autozone / O'Reilly have scanners and will pull your trouble codes for free.
11-01-12, 12:03 PM
#3
Driver School Candidate
Thread Starter
Okay. Had someone checking it out yesterday and said that no codes were showing up. Then he said that he was going to try another scanner. So that's when I stopped him from going any further but due to your suggestion I will give him another shot. thanks Mann.
11-01-12, 12:17 PM
#4
Lexus Test Driver
wait....the GX is full time 4wd with the ability to lock the center diff. Are you referring to that center diff lock?
I doubt it would throw fault codes for that. You shouldnt try to lock the center diff while on pavement either. If you try to take a turn on anything but loose soil/grass, you run the serious risk of damaging the driveline.
Under normal circumstances, when you make a turn in a vehicle, the outside tire has to spin faster to keep up with the inside tire. When you lock your center diff, you're essentially not allowing that outside wheel to spin at its own speed, and something will eventually break.
If,after your press the center diff lock button, the light on the dash just blinks and blinks without then staying steady lit with VSC off, it's possible the actuator in the center diff is frozen. I'd try starting in park, pressing the button waiting for a second to see if it engages. If it doesnt, put it in D and drive forward just a bit, then put it in reverse and drive slowly. Dont turn the wheel while moving at all when its trying to engage and when the center diff is engaged while on solid surfaces.
I doubt it would throw fault codes for that. You shouldnt try to lock the center diff while on pavement either. If you try to take a turn on anything but loose soil/grass, you run the serious risk of damaging the driveline.
Under normal circumstances, when you make a turn in a vehicle, the outside tire has to spin faster to keep up with the inside tire. When you lock your center diff, you're essentially not allowing that outside wheel to spin at its own speed, and something will eventually break.
If,after your press the center diff lock button, the light on the dash just blinks and blinks without then staying steady lit with VSC off, it's possible the actuator in the center diff is frozen. I'd try starting in park, pressing the button waiting for a second to see if it engages. If it doesnt, put it in D and drive forward just a bit, then put it in reverse and drive slowly. Dont turn the wheel while moving at all when its trying to engage and when the center diff is engaged while on solid surfaces.
11-01-12, 12:42 PM
#5
Driver School Candidate
Thread Starter
Thanks for that reply, but I think I already tried that because that is what the Lexus service manager suggested. I am aware that doing such on hard surfaces isn't recommended but I was just trying to see if the 4wd would engage since I hadn't checked it before purchase. Now don't beat me up over this because I have been there, done that. I will try what you suggest again. ? Have you heard of the vacuum switch on the transfer case possibly going bad or is that where the actuator is even located? I appreciate any more comments.
Last edited by rtrdriver; 11-01-12 at 01:06 PM.
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11-02-12, 08:51 AM
#8
That is because all GX470 are Full time four wheel drive with a selectable transfer case, which means if the transfer case were not engaging you would not be moving at all(stuck in neutral).
Transfer case control is the lever(H-N-L) right of your main shift lever. Try shifting the main lever to Neutral then transfer case to neutral(N) and then the main shift lever to Drive, you will find the vehicle goes nowhere even though the transmission is in 'D', this is because your vehicle is Full time four wheel drive.
Under normal driving conditions(center diff unlocked) you will have power to minimum of one wheel, when the center diff IS locked you will have power to minimum of two wheels.
The center diff lock forces the front and rear drive shafts to turn at the same speed.
The center diff lock is completely independent of the transfer case.
Its sounds like the center diff lock actuator is frozen, it may need to be worked a little more, try rocking back and forth a little more, if not you need a new actuator.
As previously mentioned, putting it up on jack stands may take some of the pressure off and free it up, otherwise it's off to the dealer for you.
I try to "exercise" my diff lock at least once a week on a soft surface to keep it from freezing up.
Good luck to you, if you are still unclear on the GX470 drive system the owners manual is a good place to start. There are also many online resources that may help you better understand the differences between "Full time four wheel drive", "Part time four wheel drive" and "All wheel Drive".
Transfer case control is the lever(H-N-L) right of your main shift lever. Try shifting the main lever to Neutral then transfer case to neutral(N) and then the main shift lever to Drive, you will find the vehicle goes nowhere even though the transmission is in 'D', this is because your vehicle is Full time four wheel drive.
Under normal driving conditions(center diff unlocked) you will have power to minimum of one wheel, when the center diff IS locked you will have power to minimum of two wheels.
The center diff lock forces the front and rear drive shafts to turn at the same speed.
The center diff lock is completely independent of the transfer case.
Its sounds like the center diff lock actuator is frozen, it may need to be worked a little more, try rocking back and forth a little more, if not you need a new actuator.
As previously mentioned, putting it up on jack stands may take some of the pressure off and free it up, otherwise it's off to the dealer for you.
I try to "exercise" my diff lock at least once a week on a soft surface to keep it from freezing up.
Good luck to you, if you are still unclear on the GX470 drive system the owners manual is a good place to start. There are also many online resources that may help you better understand the differences between "Full time four wheel drive", "Part time four wheel drive" and "All wheel Drive".
11-02-12, 01:07 PM
#10
RT could you tell me the light blink you have quoted, which exactly it is, is it the Check Engine Lite or 4WD. Because Typical Malfunction thresholds would be if the enabling condition of the neutral position switch going U/S ( switch being the failure)
11-02-12, 01:39 PM
#11
Driver School Candidate
Thread Starter
4wd light blinking
, and please don't take offense.Wouldn't a fault code be present in case of a switch failure? Are you talking the neutral position switch for the transfer case or the transmission? They both have a neutral. Also I've been told, and since not having experienced it, that the 4wd light is supposed to be solidly lit once the front diff lock is engaged, correct?
11-02-12, 03:23 PM
#12
Ok RT to make it easier to understand. Ok do the following inspection. ( Require 2 person to do this job - One within the Truck and one outside.
1. Turn the igntion switch OFF and set the parking brake.
2. Using a rigid jack, jack up the truck so that the 4 wheels do not touch the ground.
3. Turn the Ignition switch ON and check that the front propeller shaft free or lock when switching the centre differential lock
How to check
Condition (a) When the Centre Differential Switch is in OFF, The Front Propeller shaft is possible to rotate.
Condition(b) When the Centre Differential Switch is in ON, It is impossible to rotate.
When the switching is impossible,jack the vehicle donw to move it back and forth and then check it again for the above condition.
4. Turn the Ignition ON
5. Check the operating sound produced by centre differential lock position operation. You should here a click sound. ( This can be acheived while one person operate the switch and other person observes below the truck. If the operating sound cannot be heard, next check the wire harness if everything is still normal you actuator needs replacement. You will not have the fault code as this is under fail safe mode that the truck continue to run.
Hope this is clear.
1. Turn the igntion switch OFF and set the parking brake.
2. Using a rigid jack, jack up the truck so that the 4 wheels do not touch the ground.
3. Turn the Ignition switch ON and check that the front propeller shaft free or lock when switching the centre differential lock
How to check
Condition (a) When the Centre Differential Switch is in OFF, The Front Propeller shaft is possible to rotate.
Condition(b) When the Centre Differential Switch is in ON, It is impossible to rotate.
When the switching is impossible,jack the vehicle donw to move it back and forth and then check it again for the above condition.
4. Turn the Ignition ON
5. Check the operating sound produced by centre differential lock position operation. You should here a click sound. ( This can be acheived while one person operate the switch and other person observes below the truck. If the operating sound cannot be heard, next check the wire harness if everything is still normal you actuator needs replacement. You will not have the fault code as this is under fail safe mode that the truck continue to run.
Hope this is clear.
Last edited by mann777; 11-02-12 at 03:29 PM.
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