Engine Coolant and Antifreeze Bittering Agent Act of 2005

Engine Coolant and Antifreeze Bittering Agent Act of 2005 - Amends the Federal Hazardous Substances Act to require the Consumer Product Safety Commission (CPSC) to: (1) commence an evaluation to determine whether there is evidence that the use of the bittering agent denatonium benzoate in engine coolant or antifreeze has an unreasonable adverse effect on the environment; and (2) publish its findings in the Federal Register.

Requires engine coolant or antifreeze that is manufactured 180 days or more after publication of the Commission's findings and that contains more than 10% ethylene glycol to include a specified concentration of denatonium benzoate to render the coolant or antifreeze unpalatable unless the Commission finds evidence that denatonium benzoate has an unreasonable adverse effect on the environment. Allows the Commission to permit use of an alternative bittering additive in lieu of denatonium benzoate if the Commission finds that it is as effective as denatonium benzoate and there is no evidence of an unreasonable adverse environmental effect.

Defines the term "unreasonable adverse effect on the environment" to mean an unreasonable risk to human health or the environment, taking into account the economic, social, and environmental costs and benefits.

Deems any engine coolant or antifreeze that is not in compliance with this Act to be a banned hazardous substance.

Requires a coolant or antifreeze manufacturer to maintain records of active ingredients of bittering agents.

Limits the liability of manufacturers, processors, distributors, recyclers, or sellers of engine coolant or antifreeze related to the inclusion of denatonium benzoate in compliance with this Act. Declares that the Act does not exempt manufactures or distributors of denatonium benzoate or an alternative bittering additive from liability related to such additive.

Preempts state or local laws that impose different requirements relating to the inclusion of a bittering agent in engine coolant or antifreeze. Declares this Act inapplicable to: (1) the sale of a motor vehicle that contains engine coolant or antifreeze; or (2) wholesale containers of 55 gallons or more of engine coolant or antifreeze.