Transmission doesn't engage

Have you had the check engine light checked? If so what are the code(s).

Here is a guide on how to get the codes

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Most auto parts suppliers can scan the vehicle's computer for free. This could be an electrical issue but it's more likely an internal mechanical problem in the transmission. The diagnostic fault code retrieved will give direction on where to start on diagnosing.

Thx Ty. I will post the codes after i return for diag check. But i suspect as much that its the transmission problem and not electrical.
In Auto transmissions, are there 'clutches' for shifts from 1-2, 2-3, 3-4? if yes, are they fixable? if it is so then im sure the 3-4 is weak or dead. interestingly, many harriers i have seen develope that problem - i dont know if its harrier transmission specific weakness.
i wonder also if there are compatible transmissions from other toyota brands for that v6 engine that i can use to replace the current one.
pardon my many questions. its that frustrating that i have thought through all those options.

Yes there are clutches, bands, valves, accumulator pistons etc....in automatic transmissions. All these parts are needed to function in the correct sequence and timing to produce a shift event (1-2, 2-3, 2-1 and so on). These parts are repairable but it is labor intensive. If you decide to remove the transmission you might as well replace the transmission or overhaul the transmission. Because either way is going to be expensive.
Call around to some transmission shops and ask about compatible transmissions available for your Harrier. They should have the information available on what transmission is installed in your vehicle so they can find the exact transmission available.
I'm not sure if this is a reoccurring failure on most Harriers?
I hope this helps
TY

Thx Ty. much appreciated. i will consider the options and see which has best benefits. where i am, there are lots of second hand transmissions and few specialists of transmissions. i am wary of buying another one and getting to the same problem as i have seen happen to some friends. Your advice is very valuable and i will certainly make a good decision off it. thx again.

Your welcome. Come again.

Dear Akan

We have the same problem in our Toyota Harrier 2002. That is "What happens is that car accelerates fine, goes to fourth gear but once I slow down and go to third or second gear and accelerate again car won't go to fourth gear, it goes up to gear three only. Also, when I switch the gear into manual, the M letter on display is flashing. Once more thing is that even though it's in manual, the car is actually in automatic mode and it's shifting gears on it's own, like it's ignoring the fact that it's set to manual." We would like to know what happened to your engine/ transmission system now, is it fixed or did you change?

Dear Akan, Ty and Selvaraj,

How's the gear transmition problem, have both of u settle it already? FYI, I just buy 2nd hand Harrier 2.2 1998 and I'm facing the same problem also...
I never reach 4th gear since I buy this car 3 days ago!!! Even I run more than 80-90 Km/Hrs...
I really worried about this, hopefully all of you already solve that problem and please advise.

Firdaus

Just change my gearbox with gearbox from japan halfcut...
Sometimes it can go until 4th gear, but mostly it got some problem...
Really make my head crack with this problem...