For most people playing with their right hand is much easier than with their left hand so this combination requires much more diligence and practice. So whenever you take a new organ piece, try to spend at least twice as much time on playing the tenor than other voices. Obviously the same applies for your pedal part.
When you can play the tenor and pedal parts separately, practice them together and play this combination over and over. The best way to play this combination is not to attempt to play the entire piece from the beginning to the end but subdivide the piece into shorter fragments of about four measures. This will help you to avoid mistakes and if you do make mistakes you will be able to correct them right away easily.
The next thing to remember about gaining tenor and pedal independence applies for church organists. Many organists who play the hymns are used to play the bass line with their pedals but at the same time play their bass line with their left hand as well. It means they double the bass line with their left hand.
In other words, they simply are playing the hymns with manuals only and adding the pedal part on top of them. This is not correct and it will slow down your left hand and pedal independence. You see, your left hand has to play different music than the pedals. My best recommendation for playing hymns is to play just the tenor part with your left hand and the bass line with your feet.
This way you will be able to achieve much better tenor and pedal independence. Obviously this independence will not happen right away - this will take many weeks and months to achieve the total freedom and flexibility. Therefore, you have to stay focused and think of your long term goal and to never give up practicing this combination.
This will help you to progress much further one step at a time every day. Most importantly, before playing tenor and pedal combination make sure you can play these parts separately without mistakes at least three times in a row.