Why is my lexus460 vac light coming on - 2007 Lexus LS 460 L Sedan

Interesting since the vac line should have vac in it instead of air pressure.
Have you checked the computer for trouble codes yet ?

If you are saying there is no vac to the controller, check the engine compartment for a broken or disconnected vac hose to the engine.

possibly a frozen vac pump behind the front bumper--or a faulty pump--or check the vac pipes going to the front diff--split or come off

REMOVE EGR VALVE CLEAN OUT THE CARBON INSIDE THE EGR VALVE PORT HOLE IN THE INTAKE MANIFOLD WHERE EGR VALVE SITS.CAREFULLY USE A PIECE OF CLOTHES RACK OR A TINY SCREW DRIVER CLEAN CARBON OUT ROUND HOLE.USE A SHOP VAC TO VACUUM UP THE DEBRIS TO KEEP FROM GETTING INSIDE INTAKE.DONT USE SHOP VAC IF YOU HAVE ANY FUEL LEAKS OR SMELL GAS FUMES UNDER THE HOOD.

make sure the vac system is operating good if vac not working properly hubs will partially engage making nasty noises.

Have the vehicle scanned for codes and do the repair according to what the codes indicate are the problem areas. Once a check engine light comes on for a particular item (eg vac trac light) that item will not operate until its code item is addressed.
There are several sensors that can affect the item illuminated on your vehicle. Have a qualified Technician do the repair.

Sounds like the transfer case is signaling the GEM OK, but best to check it.
Jack up and support the front of the truck with jack stands ( and chock the wheels, normal safety precautions )
Turn the key to the on position ( do not start ).
Turn the switch to 4H, after the clicks are done and the cluster indicates 4x4, check the front drive shaft.

If the front drive shaft will not turn, it could be a problem with the vacuum motor or the vac solenoids, or the mechanics in the front axle.

If the front shaft will still turn, the problem is in the transfer case.

I am leaning towards the vac motor on the front, the vac lines, or the vac solenoids.

After the test above, lower the truck, start the truck ( wheels chocked, person have the parking brake on, and foot on the brake, safety precautions ) , and have someone turn the ESOF switch to 4H. The vac motor is the disc on the front axle. This should move when 4H is selected.


You can check vac on the pink and blue lines.
Pink is 4WD vac on the hose.
Blue is 2WD vac on the hose.
Should be able to draw vac on the line, and have it hold with a mighty vac or other vacuum pump & gauge.

Starting with the vac reservoir behind the battery box, working towards the IWE, check for cracks in the vac lines and that the check valves are working.

You can place a vac gauge on the IWE vac input, and check to see if it holds vac as a first step. This is the rough outline of the IWE vac components

Check to see if the front diff is being engaged. Ther is a vac switch that come from the transfer case. It sits right on top has 3 lines. One line is vac input the other is vac output the third is a vent. When you push the 4wd button that switch allows the vac to the front diff. The front diff actuator is under the battery. Check to see if the actuator is moving if not check to see if the switch is any good by checking vac on the actutor line. You can doo this with out taking out the battery. You will see a line that goes from the back of the engine up the right side then under the batt. It is covered by wire loom. Cut in to it and see if there is vac. If not check to see the switch works. If there is then check to see if the actuator is torn( actuator looks like a cruse control actuator) or the cable to the front diff is stuck.

pull out your courtesy lamp and ATC fuses for 1 minute then reinstall then cycle key on and off 5 times this will reset the 4x4 computer and should fix your problem. and for that question by boscia they do not have locking hubs manual or automatic.