The CAPA findings, which were cited by the Alliance of American Insurers, are the latest event in the parts controversy that has been a major issue for insurers since 1999. State Farm Insurance was hit then with a $1 billion judgment for failing to tell customers it was repairing cars with generic parts that an Illinois jury found to be inferior.

The Alliance mentioned that Washington, D.C.-based CAPA, since 1992 has used Entela Labs, of Grand Rapids, Mich. Entela, the Alliance said, is "the same lab used by car companies, to develop standards and inspect aftermarket parts."

Entela did not respond immediately to a request for the names of auto manufacturers who are its customers. A lab spokeswoman said names of its clients are generally not publicized.

The Alliance announcement applauding the CAPA findings said it has "long supported the efforts" of the group.

In fact, CAPA is funded 50 percent by insurers and 50 percent by parts manufacturers.

CAPA says members include repairers, auto parts distributors and the consumer groups, Advocates for Highway and Auto Safety and Center for Auto Safety.

CAPA rates aftermarket generic parts for fit, form, finish, material content and corrosion resistance. The organization said its latest tests were done to ensure parts bearing the CAPA Quality Seal were equal to or better than car company service parts.

CAPA said parts that exhibit the types of problems encountered in the car company service parts "will not be certified. Only after the problems are corrected and the part passes a subsequent vehicle test fit will the part become CAPA certified.

"This essentially means that CAPA certified parts are of higher quality than the car company service parts randomly selected in the marketplace. There is currently no independent quality certification for care company service parts."

CAPA gave the following list of makers with highest failure rates:

General Motors, 467 parts tested- 65 percent failure rate; Ford, 440 parts tested, 60 percent failure rate; Chrysler, 295 parts tested, 47 percent failure rate; Nissan, 141 parts tested, 41 percent failure rate; Toyota, 236 parts tested, 39 percent failure rate, and Honda, 227 parts tested, 27 percent failure rate.

General Motors was on a manufacturing break this week and was unavailable for comment. A Ford spokesperson had no immediate response, but promised there would be one.

In a statement, Jack Gillis, CAPA executive director, said repairers want parts that fit correctly the first time and "they don't want to be the ?testing labs' for part manufacturers."

Kirk Hansen director of claims for the Alliance, commenting on the CAPA finding said, "For years defenders of so-called 'genuine' replacement auto parts have touted their supposed superior quality over certified generic replacement parts. However, as this study clearly shows, many of these parts produced by auto manufacturers are often inferior to certified generic parts. In fact, half of the auto manufacturers' parts wouldn't qualify for CAPA certification.

"It has long been the Alliance's contention that certified generic automobile replacement parts, although less expensive, are superior to car company replacement parts. This study further confirms our position," Mr. Hansen said.

The Alliance said that since 1982 it has conducted numerous replacement part studies using a variety of automobile models to demonstrate the excessive cost of car company parts and that the cost of rebuilding a vehicle with "genuine" car company parts "generally triples the original cost."

In May, the Alliance noted a study finding that CAPA had complaints on only 0.02 percent of the approximately 1.5 million parts it certified in 2001.