error code 21

Hi guys , I am trying to clear error codes from my 2004 patrol and an error code of 21 just wont clear i believe it has something to do with the timing control valve. When i get home tomorrow night i am going to disconnect both batteries for 24 hours and see if that works, can anybody think of anything else i could try? Thanks

H guys just an update i disconnected the batteries for 24 hrs but it did not do anything. so i will have to think what to do next

Welcome to the forum. Have you downloaded the manual available on this forum?