Just driving home from shopping and came to a big hill and lost drive , management light came on fault code ( P0730 incorrect gear ratio ) barely got home the description of the fault is low fluid or electrical problem , also made a really funny wiring noise like a buzzing noise I've left it a few minutes and cleared the fault noise has now gone , noise was also there when not in drive and when engine running but noise has gone now , so I'm wondering if it's just low on fluid ? Been noticing over the last few weeks gear changes have not been as smooth as the used to be , do I need to buy a dipstick to check the transmission oil level ? Also how do I do it ? Engine running or not ? I may have a oil leak not checked yet as it's too wet today any advice or help would be much appreciated it's a 2.6 car 2003 .