what do 2TR-FE / 1TR-FE mean in the manual?

Making some changes to this Base model, I finally broke down and paid for the factory Wiring Book. It takes a bit of effort to learn their system and symbology, and I am still in that process. As I was using the Cruise section, I noticed the "same" diagram shown again a few pages down. I am sure this was to show 2 different models, or options, or ???? What WAS obvious was the top of these 2 sections were marked. One had 2TR-FE, which seemed to match my truck best, the other section had 1TR-FE at the top, and I could see things that did not make sense for my truck. I hate to ask a stupid question, but looking at the front of the book, definitions, etc, I cannot find any reference to those identifiers. Does anyone here know what those refer to?

 

Wow,that was fast!! Why didn't they just say so.....?? Thanks!

 

The 1TR-FE is the four cylinder motor used in the Hilux.

The 1TR-FE is a 1,998 cc I4 gasoline engine. It features DOHC, 16 valves and VVT-i . Its power is 136 hp (101 kW) at 5,600 rpm, and 18.6 kg m (182 N·m) of torque at 4,000 rpm with redline of 6000 rpm.

The 2TR-FE is used in the Tacoma.

The 2TR-FE is a 2693 cc I4 gasoline engine. It features DOHC, 16 valves and VVT-i . Its power is 159 hp (119 kW) at 5,200 rpm, and 180 lbf·ft (244 N·m) of torque at 3,800 rpm with redline of 5500 rpm. The bore and stroke are 95 mm × 95 mm.

 

Ok, so both the TR refs are 4 cylinders? I had not noticed any GR references, for the 6 cyl.
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This book is labeled 2009 Tacoma Wiring Manual. I would not expect it to show 1st Gen trucks right? Anyhow, 2TR-FE is what I will look for for when there is a difference to consider. I do wonder how they came up with that I.D. label. Must be some kind of engineering term.