Hi,

The majority of the time when you have this issue it is caused by the freewheel clutch solenoid pack, located on the right hand front fender. It is a pair of solenoids mounted together on a bracket. This solenoid pack is what controls the actuator where the front diff switch is located that you replaced.

To properly diagnose the problem however you will need to scan the codes in the 4WD system. The flashing 4WD light is the equivalent to a service engine soon light, just for the 4WD system.
To scan the system you will need either a Mitsubishi scan tool or other high-end scan tool capable of accessing the 4WD ecu. The alternative to this is to scan the codes manually. To do this you will need to locate the OBDII connector and connect pins 1 and 4 together and turn the ignition key on and the center diff light will flash the codes at you.... one long flash followed by two short flashes would indicate a 12, for example.

Once you have the codes set in the system that are causing the light to flash, you will be better equipped to correct the problem, as there are many factors that can cause malfunctions in the 4WD system.

Double check your wire, it should be Blue/White. If you never have voltage here, in all likelihood you have either damaged wiring or a failed 4WD ecu. While it is possible the fused power to the 4WD ecu could be blown, it is highly unlikely that you would still have fault indication.
It should be known that this wire will NOT have voltage at all times.

There are no relays in the system, as there is no need for them (entire system is low voltage).

4WD ecu is fused by #7 and #11 fuses in the in-dash fuse box, both are 10A.
Worth noting is a failure of fuse #7 will result in an air conditioning malfunction and an inoperable rear defogger.... so if those work, the fuse is good.
A failure of fuse #11 will result in malfunction of the ABS, dome light, and power locks systems... so if those work, the fuse is good.

I would still strongly advise that you recover the codes from the system just to be sure you know what it "thinks" is wrong, just as an aid.

Here is the diagram you requested for the entire system:

That is peculiar, however the fuse box designations do change from year to year whereas the schematic is not updated. Just use the shared circuits I listed above to test them if your fuse map differs.

The 4WD ecu is mounted in the kick panel to the side of the glovebox. It is a small box with a single connector on it.

Edited by Doug C on 1/21/2011 at 2:02 AM EST

This unit can not be bench tested.
You need to use a scan tool to manually activate the outputs and monitor the inputs.

Alternately, since you are primarily concerned with no voltage at the solenoid, you can check the output wire at the ecu for voltage on and off as you set the drive line shifter between 2H and 4L/4H and creep forward to make sure it alternates as you change position. If it does not, the ecu driver for the solenoid is possibly failed. If it does, then the voltage should be checked again at the solenoid. If it is not at the solenoid, you have damaged wiring between them. If it does, you are headed the wrong direction, and again should just read the codes to see what is failing.

Hi,
The pin configuration was in the diagram I already sent you.

pin 1 yellow/red freewheel clutch switch input signal (at harness ground when switch closed)
pin 2 yellow/red 4wd detect switch input (at harness ground when switch closed)
pin 3 blue/white 12v power
pin 4 yellow/white VSS signal
pin 6 blue/yellow hi/lo range switch (at harness ground when switch closed)
pin 7 blue/white freewheel solenoid power out
pin 8 black ground

Power to the ecu comes through the ignition switch on the same feed as your rear defogger switch, AC, etc.

The colors sometimes vary by year, so use the pin #s to correlate location to function if you have any differences.
pin 10 yellow/blue ground out to combination meter (turns light on)

Hi,

Did you ever check the codes like I recommended? I highly doubt that you need a ECU. I have seen maybe one of these fail ever.

Pin 4 VSS is your speed sensor signal. You will need an oscilloscope to test this. It is a 12V square wave signal, roughly 5 per second, with increasing range/duration with vehicle speed. If your speedometer works, this should not be a concern.

If you find you do need the ECU. these should be readily available from any dealer. This ECU was used for about 12 years in some markets, and is the same one used in all distributions. US dealers sell this part for about $50. There is no compatible part supercession, it must be this part number... as I said before, these almost never fail, so there has been no reason to update them with newer revisions.

Sure, go to mentormitsubishi.com, select Service and Part ~> Order Parts.
A TradeMotion website will open, on the left side 1/3 of the way down is a spot to type in the part number manually; insert MR222642 there and select "Mitsubishi" and click search and you will be able to order the item.

If there is no power at #7 at any time, that is pretty suspect.

We can continue talking here either way. Please do click Accept unless you are fully satisfied with my assistance though. And as I said, we can continue talking in either case.

A sticking detection switch (4wd, lo/hi) could cause this to occur. I would check pins 2 and 6 and make sure they receive ground on and off as you put the shifter from 2H to 4L and to 4H and no ground when in 2H.
A stuck freewheel engage switch (or possibly disconnected) would cause this as well.

It is a peculiar situation for sure; I don't recall ever having run into one of these that cut power to the solenoid pack without any other symptoms.

No, you will need a scan tool capable of manufacturer systems (TCM, ABS). That unit (and most inexpensive ones) will only read OBDII, which is engine-only.

A unit like that is probably capable of accessing them with the right software, but you have to find the right software (if it even exists).

No, VAG scan tools only work on VW family cars (VAG= VolkswagenAudiGroup)

Hi,

I am not familiar with that scanner to be precise, however browsing their website it does look like it will likely do anything you need it to do. While it doesn't specify several computers, that may be just to save space. It does specify ABS, TCM "code" access, so at the very least you will be able to scan and clear codes in those systems, you may not be able to read data lists/live data in those systems, but that, while important, is not as big a deal as being able to read codes out.

It looks like a pretty solid choice; if you do end up getting it I would appreciate if you let me know your opinion, as I have not dealt with this brand scan tool before.

It is just below the dash on the driver side; it is a 16 pin two row connector.

Here is the location on left hand drive models. If you have a right hand drive, it should be roughly a mirror image.

Oh I'm sorry I misunderstood.

The OBD/DLC3 connector isn't going to have anything useful to offer you in this situation; The purpose of grounding those wires is that it activates the self diagnostics on the TCM and ABS systems.

Nonetheless, here is the pin out for the DLC3/OBDII connector:

1 PCM Data (undocumented, scantool connect detect)
4 Ground
5 Ground
7 PCM Data (BUS line)
14 VSS signal
16 Dedicated 12V