Why does the 2UZ-FE have the "T" timing mark but not reference them in the FSM (1 Viewer)

[WestTX28]

I've owned four vehicles with 2UZ engines and between them have replaced the timing belt several times. This weekend I helped a friend replace the TB/WP on his truck. He was most concerned with the cam crank timing aspect of it as I think most people who have never done it are. I've always followed the FSM and or Aisin provided instructions and don't think there has ever been a contradiction between those. I instructed him to do the same which we did and all went well. But the big glairing potentially confusing component of this whole procedure is those "T" marks.
They are never mentioned in the FSM or Aisin timing belt replacement procedure and I couldn't find reference to them in other parts of the manual either.
Does anyone know what they are actually for? There must be some significance especially since they match up to nub on the crank cover . I know a lot of folks use it for the timing belt replacement position and they very well may be right. The FSM always says about 50 degrees which to me says just get it close but that's most definitely not where the 'T' marks are. Everything is so technically spelled out why is there no reference to those marks? I've seen the videos of Toyota techs using the "T"s but from what reference source?
Just reflecting on the job and been thinking about it all day and am just genuinely curious is anyone knows.

 

[GVegasG]

I was wondering same thing when I was getting ready to do on 04 LC. Ended up using T marks and it worked out.

 

[abuck99]

Theres been debate on the forum on the use of the T marks- not disclosed in the FSM but they are commonly used. Its the set up to those reference marks that is key to a successful outcome.

I read a good tutorial a few weeks ago by a Toyota tech who uses the T marks- I posted the link to his video in another thread.
Here- T Marks

 

[WestTX28]

abuck99, yeah, I've seen the threads and debates here over the years. It just seems that if the T marks were referenced somewhere by Toyota there wouldn't be this ambiguity and confusion. It's clearly got to be a significant timing position. Just so freaking weird it's not documented.

 

[AlpineAccess]

My understanding is TDC is at the cam markings, but the T marks are an optimal positiion for preventing accidental cam rotation. I have done my timing belt at both sets of marks on my 99 and on several other early model 100s, and after rotating the motor by hand two full revolutions the marks have lined up all times.

On my VVTi Tundra there was TDC and ATDC as well, and I went to TDC and had a cam spin. It was easy to rotate back but if I'd had my fingers in the belt when it spun it would have been a bad day. So keep that in mind.