Prospect

Should be a dirty great big grommet there somewhere where the main loom enters the cabin... Not familiar with Prado's, but on the Patrol (GU), this is under the brake booster.. also another on LHS behind wheel-arch.. Patrol also has a blank grommet in the middle of the firewall..
If the Prado has no blanked-off holes, you should be able to feed a wire through beside the main loom, otherwise, just poke a (small) hole in the rubber grommet & feed the wire through that..
Hope this helps, Good luck!
Ed. C.

Ed got it in one.
You will see where other wiring runs through the firewall. Use a piece of wire with some dishwashing detergent on it to make a SMALL (note the word SMALL) hole in the rubber grommet under the other wires.
BUT make sure you have someone under the dash with a torch so they can see where the hole is.
You'll manage.
Remember, gently does it.
A bull at a gate can damage quite a bit.

Haldo

Drill a neat little hole...........fit a rubber grommet into the hole..........pass the wire through the grommet......easy.......

Cheers,
Willie
Never a dull moment

Drill a hole - ? When I went to try that in the Jack, couldn't find anywhere that a cordless drill could be set up AND I could ascertain what was on the other side of the FW. Drill by all means, but be damn sure you know where that drill bit is going. Loom grommet method fixed me up.Get me outa these suburbs !

hi mg , In the past i used to design and install a lot of high powered car stereo systems etc. (still do a bit) and have a set of wire grommet" pokers" that are nothing more than pieces of aluminium tube with one end smooth and the other end chamfered about 4 inches long in various diameters. all you do is pierce a small hole in one of the existing grommets and using a bit of silicone / detergent etc work the pipe through from whatever side is easiest. you can then run wire through with ease to where you need it. just remember to remove the pipe from the grommet before you terminate the end of the cable !! The grommet will then re-form around the cable perfectly.
When i did some work for a while with a Holden dealer they had not seen the idea and always struggled to get wiring through the firewall, they loved it !! we ended up making heaps of tool sets using old antenna masts and they have never looked back. I have used this system for many years with total sucess with wiring from 14g up to 4g wiring (huge) and love it.. Hope this helps with your future projects.. Brad