I have a 99 montero sport runs and drives fine. 4x4 light flashes full time abs some times. I have diagnosed everything from the interlock switch at pumpkin to the freewheel actuator to the minature vacum pumps to the reverse switch. this is a customers car so i dont have it at this time. When i have the car running it seems like both vacum pumps that plumb to the freewheel actuator are both running. Does one vacum acutor just go to operat the disengage? Ane the other to engage? I have checked fuses and the 4x4 hi and low work just fine and light stays on solid when engaged to hi and low. Would the fluid level in the front diff cause this problem? I personally would think not. I know the interlock switch works just fine and the vacum actuators and the freewheel actuator. what are my next steps????? thanks Jeremy

 

The main source of failure for flashing 4WD lights is the front axle drive solenoid valve. If the system is not used, and you suddenly decide to use it, the front axle sometimes does not disengage, causing the lights to flash. I've had to replace mine once as well.

The part is located on the passenger side of the vehicle, above the wheel well, just under the air box. Part number is MB620532, costs about $55, although I'm not 100% sure yours is exactly the same part number. Is the vehicle equipped with F/T, P/T or Super Select/Active-Trac 4WD?

 

Well, I've had two 4x4 Montero Sports, a 1997 XLS and a 1999 Limited (which I still have at 210,000 miles!) and this has always been a result of a faulty freewheel engagement switch on the front diff from my experience. It can also be the 2/4WD switch located on top of the transfer case. The ABS system depends on input from these switches to determine what ABS mode it will use. If something isn't right or in conflict, it will trigger the ABS light. I wouldn't bother spending the time to test the switches. Time spent on replacing them is minimal. Start with the front diff switch. If that doesn't solve it, replace the one on the T-case. They'll go bad eventually anyway if the 4WD isn't engaged regularly.

 

Would this problem also exist if you hit a pot-hole?

 

I have this problem and tested the two solinoids on the wheel well under the airbox and one was bad, no ohm reading. The lights just started blinking for no reason as I didnt put it into 4wd. Just one day starting it up the were blinking and I think the front drive shafts are turning at least it sounds like it. I called the dealer and each is $74 and he said there is another on the transfer case for 4low which is $40. I guess I should replace all of them...

Ok, orded it online for 99.89. I got the diagram and it is both solenoids.
http://www.mitsubishiparts.com/oe_parts_catalog.html
put in
2001
mitsubish
montero
go to
front drive axle
Drive axles
Differntial
solenoid valve
MSRP $124.15
your price $89.39

 

the solenoid pack by the wheelwell should fix this problem. happens on the fullsize too. pretty common. there is a T.S.B for the sport and the full size that will tell you to replace all the switches and the seal rings for them on top of the transfer case. i would go with the solenoid pack first. fixed many by doing that