So little of the capacity at Princeton is being used that the company's honorary chairman, Shoichiro Toyoda, visited the site in October, the newspaper reported, citing an unnamed company official.
However, the Journal added, the company plans no layoffs at Princeton.
The Princeton plant can turn out 100,000 Tundras a year, although it's unclear how much of the capacity is unused. The line also can assemble the Sequoia sport-utility vehicle. San Antonio has twice the capacity to assemble Tundras.
Toyota's concerns come as the company experiences a sales slump that is its worst since the early 1980s. The company's sales fell 10 percent in March from a year earlier.