According to documents filed with the National Highway Traffic Safety Administration, the fuel pipes in the the engine compartment of the vehicles were manufactured with a nickel phosphate plating to protect against corrosion. Toyota suspects that some were produced with plating particles on the gasket seating surface where the fuel pressure sensor is installed.
This could result in the joint not sealing properly between the pressure sensor and the fuel line. During vehicle operation, fuel could leak past the gasket and increase the risk of a vehicle fire.
Automakers have recalled about 55 million vehicles in the U.S. this year, breaking the annual record set in 2004.