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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8594
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I have a 2000 Montero Sport that the 4wd is not working

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I have a 2000 Montero Sport that the 4wd is not working correctly. I need someone to walk me thru the diagnostics


What exactly is the 4WD doing? For example are you having difficulty moving the shifter, or does the shifter work OK but the 4WD light continues to blink when in 4WD (or solid in 4WD but won't go out in 2WD) etc?

Customer: replied 9 months ago.
4-wd light does not come on. I checked pins 1 and 2 on the 4wd ecu and they never change. i put grounded pin 1 on the ecu and the light comes on so its not working before this - its kind of daunting to remove the sensors on the transfer case so I am wondering if there's a way to check 4x4 operation without having to remove the sensors. The transfer case shifts smoothly and if i put it between 4hi and 4 low and put it in gear it is def doing something


The sensors are nearly never the problem on these 4WDs... while in rare occasions they will fail (normally when the vehicle gets submerged regularly), they will not prevent the 4WD from working entirely anyway so I wouldn't be thinking of anything in that direction.

When you turn the key to On, does the 4WD light do a bulb test for 3-5 seconds (like the brake and oil lights do etc)?

If you do not see a bulb test, then please check for power to the ecu by unplugging it, then connecting a meter or test light between a solid chassis ground and pin 3 (blue wire with a white stripe) with the key on. If there is no power there, verify in-dash fuse 11 (10A) is good. If there is power there, then check for voltage again this time by measuring between pin 3 (still blue wire with white stripe) and pin 8 (black wire) with the key on.

Customer: replied 9 months ago.
12V Chassis to pin 3 GOOD
12V pin 8 to pin3 GOOD.
Customer: replied 9 months ago.
I do see the bulb test.


So power and ground to the ecu are OK and the ecu is powering up, those are good signs.

At this point there is a high probability of a switch failure unfortunately, rare as that is. While the ecu could be at fault, generally when they fail they no longer bulb test (when they fail they don't function in any capacity). If you had a solenoid failure (most common cause for 4WD malfunction) you would get the flashing 4WD light when you attempted one range or the other.

The speed sensors and front axle switch etc are all non-issues since they would not affect the light operation.

The prime suspect I would have would be 4WD detection switch that determines if the shifter is in 2WD (or AWD) or if it is in 4H or 4L. You can test this by checking for ground on pin 2 (yellow/red stripe wire) when the shifter is moved to a 4WD range (key can be off). While not likely an issue, the 4L/4H detection switch can be tested the same way... check for ground on pin 6 (blue/yellow stripe wire) and it should go on/off ground as you switch back and forth between 4L and 4H. Again this is less likely than the 4WD detection switch though.

These tests can also be performed on a live data scan tool with Mitsubishi-specific transfer (4WD) ecu support.

If you are seeing proper ground when the shifter goes into 4WD... I would suspect either a wiring issue or a faulty transfer ecu.

Customer: replied 9 months ago.
I tested pin 2. No change no matter what position on transfer case - i did put a needle thru the wire and shorted it to ground - the light began to flash - It stopped once but then began flashing again. (What I am trying to do is determine if there are multiple issues and fix them all at once). For example if the TC is bad no sense in buying sensors. so if 4wd is faked and its in 4hi what else needs to happen to engage the 4wd. BTW I have seen multiple mentions of AWD vs 2wd what enables that?
Customer: replied 9 months ago.
I tested pin 6 it works but seems like it has high resistance (80 ohms). I checked for voltage on the blue and yellow solenoids while the 4wd light was flashing and it doesn't work. what schematic shows the solenoids for the front diff actuator? I didn't see it in the 4wd ecu

If there is question as to the condition of the transfer case (like you just bought the vehicle), I could see that point... otherwise I wouldn't worry about it if it was working prior etc. It is unlikely to have had multiple failures.

As far as the transfer cases go... the shifter operation is your #1 indicator of condition; if it moves solidly between ranges, that is what you want. You don't want it too smooth (the shifter bushings fail and this happens, as well as forks bend and this happens), nor do you want harsh obstructions when shifting of course. The second indicator is noise while driving... and this will about always be heard in 2WD as well.

For 4WD to work you will have the following conditions:

Shifter goes to a 4WD range, 4WD engage switch closes and grounds ecu.

4WD light begins flashing.

Ecu sends 12V to the two front axle solenoids (free wheel clutch solenoid pack) on pin 7 (blue/white stripe).

Solenoids reverse flow and vacuum switches from pulling the front axle out of 4WD to pulling the front axle into 4WD.

Front axle detection switch changes position from 2WD to 4WD (or reverse of course), signal from front axle switch shows a matching position to 4WD engage switch.

Light goes solid indicating 4WD engaged.

AWD versus 4WD depends on your model. The easy way to tell is looking at the shift lever. If you have traditional 4WD it will show 4H-4L-2H. If you have AWD it will show 4H-4L-AWD. The AWD models all have a beefy shift knob; 4WD models some have a beefy shift knob others have a small rubber molded knob.

AWD models use a viscous coupler not found on 4WD models.

Don't worry about pin 6... pin 2 not grounding is where you are worried about. I would be checking the wiring for issues, and if nothing surprising is found, replace that 4WD detection switch.

Here is the 4WD engage detection switch location. You would want to do a continuity test between the yellow/red wire on the switch connector and the yellow/red wire on the ecu connector to make sure the wiring is OK. If you get 0.000 (perfect continuity) then the wiring is fine and you just need to replace the switch. If you see considerable resistance (more than single digit ohms), then there is a wiring problem to address somewhere between them.

Customer: replied 9 months ago.
ok - its a new to me vehicle so thats my reason for thorough investigation - i am 90% sure the 4wd shift sensor is bad. (i have faked it and now have a flashing light) So should I have 12V at the solenoids near the passenger wheel well? one is yellow and the other is blue. (they have a dot on them).
Customer: replied 9 months ago.
its dark here now so i will resume tomorrow.

Correct, you should have 12V to the solenoids when the 4WD engage switch is closed (or that pin grounded and ecu plugged in of course).

Both solenoids get the same feed from pin 7 blue/white on the ecu plug, it just splits off like it shows in the schematic I attached.

Customer: replied 9 months ago.
Thanks - what is the section and page for that schematic mine is very different. I am trying to figure out why.
It should be shown in line as an attachment you will need to click on.
Customer: replied 9 months ago.
oh i can see your attachment - but my manual is different
Customer: replied 9 months ago.
my manual has it on 90-152
Mine is from Mitsubishi directly for a 2000 sport including any updates from Mitsubishi, it should be the accurate one.
Customer: replied 9 months ago.
I bridged pin 3 and pin 7 on the control and 4wd still didnot engage - so far its the 4x4 switch and now the solenoid is suspect. Is there a easy way to bypass everything and test the 4x4 mechanically?
Please do not go randomly shorting wires together, you risk causing MUCH more serious problems that way. I have provided you the only things you need to do yesterday.
If you wish to manually try to test the 4wd without repairing the switch input issue (be it wiring or switch), do exactly as we discussed yesterday and ground ONLY the 4wd detection switch input and leave all else the same and place it into 4wd.
With regard to the 3/7 bridging that would only supply power to the solenoid pack but all other inputs need to work for 4wd to engage.
As for the solenoid packs... Yeah they fail a lot, it wouldn't be surprising.
You should have about 35 ohms across each coil and they should hold/release vacuum properly when power is added/removed manually. A hand vacuum pump is required to test that though... Blowing through it is not sufficient.
The hand vacuum pump can also be used to bypass the electronic/vacuum control. On the front axle you'll see a diaphragm/bellows and actuator rod on the passenger side of the diff. One port on the diaphragm pulls the rod into 2wd and the other into 4wd. Use the hand pull to pull it into 4wd and make sure it holds indicating both the actuator engages ok and the diaphragm holds vacuum, then choose a 4wd range and test it.
Note the lights may go nuts on the dash, that is ok if they do. With the 4wd switch bad they may not though.
Customer: replied 9 months ago.
Thanks - the hand pump thing is what i'll try - i just want to make sure it CAN go into 4wd before i buy a bunch of parts - if need to replace the front end or the transfer case - they'll come with the hardware (used from a junk yard).
Customer: replied 9 months ago.
does the vacuum hose for that system attach to the top of the intake near the firewall drivers side?

Eventually yes... all vacuum originates at the intake manifold. If I recall, the 2000s had a vertical nipple on the drivers rear corner of the intake where a hose connects to the firewall pipe, which leads down and across to the passenger frame rail.

Customer: replied 9 months ago.
today the 4x4 switch decided to work so now when i put it in 4Hi or 4low it flashes for a bit then goes solid - still not engaging the front axles - i know this because i can't reverse up a slight incline without getting stuck.

Best to elevate all four wheels off the ground to check rather than expectations of the vehicles abilities. While you may be right, that way is more accurate in telling what is/isn't happening.

If the front end is not engaging then check your actuator is holding vacuum and not leaking. If it is, then pull the cover off the differential and see if the fork is engaging properly not jamming or broken and so forth.

If it is engaging properly and locking both the front wheels to the front propeller shaft, then expect a problem in the transfer case.

Customer: replied 9 months ago.
to pull the cover off the diff i will have to change the gear oil or are you talking about something else?

No that is correct, you will lose your gear oil when you remove the cover.

I would say if you don't want to do that (but keep in mind if the history of the vehicle is unknown, odds are the fluid is way over due anyway), what I would do is use the hand vacuum pump to engage 4WD with the car off, then verify that the front wheels both spin the front propeller shaft. At the least that would tell you the differential is engaging (it is a shift fork set up like you would see inside a manual transmission that engages the two sides of the diff together when the actuator is applied). If it does, then you know you are in the transfer case most likely; if it does not you know that differential is likely coming out depending on if the actuator diaphragm holds vacuum etc.

Customer: replied 9 months ago.

You're welcome!

Customer: replied 9 months ago.
I've ordered a hand vacuum pump ( i can't find my own) it should be here tomorrow - ill continue when i get that done.


Customer: replied 9 months ago.
Got the vacuum pump - when i hook it up at the engine it slowly leaks down. Its cold today so i didn't get underneath and hook it to the actuator. I did disconnect the blue input side and plugged it. it held vacuum so i know that from the engine to the solenoid including the yellow solenoid the vacuum pressure holds. so its the blue side - and possibly the solenioid.

No problem. Test it when you are able. Note that I am on the south east coast of Florida and we have a major storm pushing through in the next 24 hours... depending on the severity (forecasting 130mph+ winds at this time), I may be without power and unable to respond immediately.

Customer: replied 9 months ago.
As i understand it - the vacuum system should not leak - right?

The 4WD system, correct. The rest, no it will leak. Remember the vacuum naturally is a result of the pulling of air through the intake valves. So in order for the system to be vacuum tight with the engine off, you would have to completely seal the throttle body shut and shut all intake and exhaust valves. Otherwise, it will leak down, that is normal.

Customer: replied 9 months ago.
But if I disconnect it from the engine and pull a vacuum at that line it should not leak down

If you are pulling from the port on the intake... it should not to any great degree. There is a lot of air to suction out before it would hold due to vacuum tank and the two solenoids venting... but yeah it should eventually hold a vacuum. I would do as I described testing at the actuator first to accomplish what you asked of me in verifying the actual axle works. Then build out from there.

While you may have a leak somewhere, I mean hoses rot a lot, the solenoids always fail eventually (if not frequently), the vacuum tank could rust out etc etc... none of that matters if the axle doesn't work anyway which was the point of starting with the vacuum tests.

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