A revolution in the way cars are made that started in a small, nondescript office building in a suburb of this Swiss city is sweeping the General Motors Corporation. Its code word, coined by a Spaniard, is "Picos."

Repeated like a shibboleth by executives at G.M.'s modest European headquarters, Picos is short for "program for improvement and cost optimization of suppliers." In essence, the term covers the mix of ruthless probing, consultation, orders and ultimatums that J. Ignacio Lopez de Arriortua used to slash the cost of parts for G.M. Europe, making it hugely profitable while its Detroit-based parent piled up losses.

Now, Mr. Lopez, an indefatigable 51-year-old engineer sometimes referred to as the "grand inquisitor" in European automotive circles, is attempting to do for G.M. in the United States what he already achieved in Europe as the executive in charge of purchasing. That is, G.M.'s new management would like to see G.M. Europe's performance, in piling up $8.54 billion in profits since 1987, repeated at home.

"He ran the European parts operation the way they now want the whole North American operation organized," said John F. Smith, vice president for planning of G.M. Europe, who is not related to John F. Smith Jr., the G.M. president. "That's why he's over there. That's his mission. And I tell you he's driven."

Named vice president for worldwide purchasing in Detroit in April, Mr. Lopez, who is 51 years old, gave a taste of his medicine on June 2 when he told a startled group of executives from G.M.'s suppliers that contracts would be reopened for bidding, that prices would be renegotiated, that G.M. would no longer favor its internal manufacturers, which supply 70 percent of components in G.M. vehicles, and that 50 percent improvements in productivity were expected by 1995.

"We were told the slate is clean," said John Kennedy, the president of Autocam, a supplier in Grand Rapids, Mich.