A Senate committee approved a plan yesterday to radically alter Maryland's planned auto-exhaust inspection program, a move that House leaders already have said they oppose.

By a vote of 5 to 3, the Constitutional and Public Law Committee sent to the full Senate a proposal to cancel the state's $67.3 million contract with a California firm to operate the program.

The panel instead approved an amended plan offered by its chairman, Sen. Norman Stone (D-Baltimore County), to allow private garages, including those not equipped for regular car inspections, to perform the tests.

Under the Stone proposal, inspections would be required every other year instead of annually as called for under the contract with Systems Control Inc.

The revised program would run six years instead of five.

But the chairman of the House Environmental Matters Committee, Del. Larry Young, (D-Baltimore), said he expects his panel to accept only minor changes in the inspection program.

Under the Stone plan, the inspection fee would be reduced from $9 to $7.50.

Of that amount, $5.50 would go to the station and $2 to the state.

An opponent of the Stone proposal, Sen. Gerald Winegrad (D-Anne Arundel), said only one of every five car owners would have to seek repairs under the current program, but abuses and fraud would change that percentage to one out of every two if the Stone plan is adopted.

The federal Environmental Protection Agency already has proposed banning some kinds of industrial development in Maryland, accusing the state of violating federal clean air laws by delaying implementation of the program until 1984.

Only motorists in the Baltimore and Washington metropolitan areas would be be required to put their cars through the inspections.