Parking break on my doosan forklift will not set and no techs available for several weeks, anything i can check?

We aren't Forklift experts here at Fixya. You need a Doosan Service Tech on that one. Any subsequent failure causing dea th becomes their responsibility.

check engine means problem so when problem fixed light will go out

I recently tried the DIY service and repair manuals from a website and it actually helped me repair transmission problem in my jcb 3cx site-master.
It would'nt move forward or reverse, engine was good both solenoids for forward and reverse worked, but still couldn't diagnose the problem.
I don't have much technical knowledge but I just followed it step-wise, and now it works perfect! covers wiring, codes, diagrams, torque specs, PCV, everything
got it from www.reliable-store.com

I suggest you get one of those manuals people get nowadays to do it yourself.. My nephew use it to repair my cummins engine and it's totally repaired now. Here's the website he bought it from.
Best Manuals

First make sure the battery is fully charged. Then check for clean battery post connections. Then check all the main fuses located in the plastic box under the hood close to the battery on top of the inner fender. You should have all dash lights if everything check out to this point and it should turn over with the key.

get the ign only feed from the ignition switch its self

IF ITS A DASH 5 TRUCK THE DRIVE AND THE LIFT CIRCUITS ARE CONNECTED ELECTRICALLY, THE PROBLEMS USUALLY THE SEAT SWITCH OR LOOM, TRY BRIDING IT OUT AT THE 2 PIN MULTI UNDER THE ENGINE COVER, YOU WILL ALSO GET THE MAST INTERLOCK LIGHT COME ON . IF ITS A DASH 3 THEN YOU WILL HAVE TO DIFFERENT PROBLEMS. CHECK ALL FUSES AND RELAYS AND SEAT SWITCH, ANYTHING OUTWITH THAT ID NEED MORE INFO AS I COULOD BANG ON ABOUT IT FOR A WHILE....

ON MANY OF THE -5 RANGE OF THE TEIR2 & TEIR3 DOOSAN TRUCKS (ORANGE IN COLOUR) HAVE FLYBY WIRE THROTTLE, YOU CAN USE DIAGNOSTICS TO READ THE CODES BUT THE TRUCK ALLOWS YOU TO READ THE FLASH CODES BY TURNING THE KEY TO THE FIRST POSITION (IGN LIGHTS ON) AND PRESSING THE ACC PEDAL UP AND DOWN FULLY 5 TIMES IN 3 SECONDS AND THE MIL LIGHT WILL FLASH OUT 3 DIGIT CODES UNTIL YOU READ A 2 DIGIT CODE WHICH IS 12 AND THATS THEM RETURNING BACK TO THE START AND THEY WILL REPEAT AGAIN. TO CLEAR THE CODES TURN THE KEY OFF AND BACK ONTO THE FIRST POSITION AND PRESS THE ACC PEDAL UP AND DOWN 10 TIMES IN 5 SECONDS TO CLEAR ALL CODES FROM THE ECU. THERE A LOT OF PHANTOM CODES THAT DOOSANS BEEN CHANGING THE SOFTWARE TO TRY AND ELIMINATE SO IT WOULD MAYBE BE A GOOD IDEA TO HAVE UR SOFTWARE UPGRADED (5MIN JOB). ALSO A LOT OF CODES ARE THROWN UP DUE TO THE WIRING LOOM THAT RUNS OVER THE INLET MANIFOLD THE RIBS ON THE SHEVIN WEAR THE WIRING IN THAT PART OF THE LOOM AND THEY SHORT AND THROW UP CONSTANT CODES. ANY ISSUES WITH CODES JUST CONTACT ME.........

its the Prindle and it needs to be set in Neutral like middle the white nob then put back in Park then run the gears see to see if they line up . hope this can help.Need to drop steering to put new one in