nsteurs

Put Comma Xstream G30 in mine, diluted 50:50 with de-ionised water.

Approved for Porsche vehicles built up from 01/1996 and 01/2009 - https://www.commaoil.com/passenger-vehicles/products/view/351

I have the NT530 (with Porsche software) and it could read & clear Alarm System codes off of my '97 986.  It has also read DME, ABS, A/C & Airbag codes too.
Not tried if it can see actual values though.

Similar thing happened to mine - clamshell raising/lowering on one side only.

On earlier cars, the outer sheath of the top drive cables can expand due to heat/age, effectively lengthening the cable and pulling the inner metal drive cable out of the roof motor.  Hence when the motor turns only one cable gets driven so only one side of the clamshell moves.

If you pull the cables off the motor, you should have about 3/4" of square-ended metal drive cable sticking out the end of the ferrule on the cable.  Mine only had about 1/4" protruding.

I removed the ferrule from the end of my cable and cut the outer sheath back a bit so when the ferrule was refitted, there was 3/4" of the inner cable sticking out.  Or you can replace the cables with later reinforced ones - the early ones have a smooth finish to the black sheath whereas the later reinforced ones have a cross-hatched pattern to them.

Note you'll have to align the mechanisms once you've sorted the cables - you can move each side's mechanism individually by operating the motor with only one cable connected at a time until you get both sides in the same relative position.  There are alignment marks on the mechanisms but you have to remove the lever arm (undo the big bolt in the middle of the lever) and then the black circular cover plate to see them.  Or eyeball it.

If the clamshell itself has been twisted if it was moved too far on one side only, you can unbolt it and GENTLY twist it back straight with the aid of an assistant; it's quite flimsy.