Auto tranny , no 4th gear

Question edited for clarity and spelling 'wat' to what and 'heard' to gears.

You need a transmission specialist or an auto-electrician with a pro grade scan tool computer to diagnose which sensor or module has failed. The test is done as you drive the vehicle and it records the live data.

that could possibly be a transmission issue that you're experiencing. mine did the o/d flashing and took it to a mechanic seems like my 4th gear was almost about done. i would recommend you turn o/d off and take it to a transmission specialist so they can make sure your tranny is fine first. if the tranny is fine then i wouldn't know what else would be the issue.

take to a autobox repair shop for them to diagnose as not the sort of thing that can be done at home

If its having difficulty moving through the gears it could be a transmission issue or the turbo could be bad which would also cause a bogging down situation.

sounds like the syncros in your tranny are toast. they are what let your car go into gear and have little teeth on them. You know they are going bad when they start grinding. Id look in a salvage yard for a new tranny or have yours rebuild. Which can be pricey. Rate my answer man!

The Transmission computer is the Achillies heel of many Mitsubishi vehicles , it sounds like your Pajero is in " limp home " mode which gives you third gear only.
See if you can borrow a replacement computer to try.
Mitsubishi scrimped on the quality of the capacitors in their computers and their failure rate is very high.
Happy hunting Marshall

not unless fifth seases to the baring's. but then it won't even go in to 4th or 5th. it's probably your sincro's that r bad between 4th and 5th.

I actually have the same problem just a few mos ago with my Pajero Fieldmaster 4M40 A/T. Is your speedometer working? My speedometer sensor is intermittently working if it does not work at all, the tranny will not shift to 4th gear no matter how hard you push the gas pedal to the limit!! I replaced the speed sensor and it goes back to normal now.

I'd check the overdrive solenoid atop of the tranny. Apply 12V + to it and see if it will go in to OD. If it does you will need to check the OD relay or temp switch. Or rewire a new switch.

Thanks,
Tom

time to consider a visit to the junk yard and fit a manual