Federal regulators vowed to continue an unprecedented crackdown on car makers when uncovering significant safety lapses, a day after unveiling a record $105 million fine and other sweeping penalties against Fiat Chrysler Automobiles NV for mishandling recalls.

U.S. Transportation Secretary Anthony Foxx on Monday said he was encouraged by ongoing dialogue with auto makers on safety problems and the implications of cutting-edge technology on the road to driverless cars.

"But it doesn't mean that if we find ourselves in a situation where enforcement action is necessary that we will not do everything we can," Mr. Foxx said. "This is what we're supposed to do."

The National Highway Traffic Safety Administration, under fire from lawmakers and others for failing to spot safety problems, is negotiating settlements with increased penalties for auto manufacturers.

For Fiat Chrysler, the $105 million penalty represents roughly the same amount as the company's most recent quarterly earnings and comes as the auto maker hunts for a merger partner and negotiates a new labor contract with the United Auto Workers union.

The auto maker also faces $150 million of legal damages stemming from a jury verdict earlier this year in a trial over a fatal Jeep fire, though the monetary award could be reduced.

The $105 million regulatory penalty includes $15 million that is deferred but could become payable if Fiat Chrysler violates terms of a consent order or federal law.

In addition to the record financial penalty against Fiat Chrysler, regulators will assign an independent monitor to audit the company's recall processes for up to four years and in some instances require vehicle repurchases, a rare punishment. Regulators hit the auto maker with a maximum $35 million fine for three broad transgressions: misleading and obstructing regulators; inadequate and lagging repairs; and failing to alert car owners to recalls in a timely manner.

NHTSA Administrator Mark Rosekind likened the independent-monitor condition to one imposed in 2014 by the Justice Department on Toyota Motor Corp. of Japan in a criminal case over sudden-acceleration issues.

Mr. Rosekind said a consent order signed by Fiat Chrysler provides "unprecedented scrutiny" of the Italian-U. S. auto maker's recall processes. Still, the auto maker could have suffered higher penalties given the number of scrutinized recalls. Regulators said they haven't referred the matter to the Justice Department, which extracted a $1.2 billion penalty in the criminal case against Toyota.

Fiat Chrysler signed a consent order acknowledging lapses spanning nearly two dozen recalls affecting more than 11 million vehicles, including older Jeeps with rear gas tanks linked to dozens of fatal fires.

The financial penalties top the $70 million assessed against Honda Motor Co. at the end of last year for lapses reporting possible safety problems and $35 million General Motors Co. paid in 2014 for failing to notify regulators in a timely manner about defective ignition switches as required under federal law. Neither company agreed to an independent monitor in signed consent orders.

"One of my priorities has been to make NHTSA a much more muscular agency," said Mr. Foxx, the transportation secretary.

As part of the sweeping Fiat Chrysler settlement, the company must offer to repurchase many pickup and heavy-duty trucks and sport-utility vehicles with model years from 2008 to 2012. The more than half a million vehicles were recalled for suspension problems that can cause a motorist to lose control.

The repurchases are limited to vehicles that haven't received repairs under existing recalls. Fiat Chrysler said repairs have been completed on over 60% of the affected vehicles, leaving less than 200,000 eligible to be repurchased. The repurchases could still prove expensive, though Fiat Chrysler has the option of then reselling them as long they are repaired first.

Fiat Chrysler said any repurchase premiums and sales incentives involved in the recall campaigns will be credited to the $20 million it agreed to spend on recall outreach. The company said it doesn't expect a significant financial impact from the expenditures.

Tim Meroney, a 65-year-old retired police officer who lives outside Monterey, Calif., within the last two weeks traded in a 2009 Ram pickup after frustrations with repairs at a local dealership and mechanic. He described recently losing control on a local highway.

"We're talking about a violent action. My wife wouldn't get in it anymore," Mr. Meroney said, adding he estimates spending roughly $4,000 on repairs. "I'm more angry at Fiat Chrysler than I can tell you without saying four-letter words."

A Fiat Chrysler spokesman declined to comment beyond noting the repurchase offers on affected vehicles are limited to those that haven't received recall repairs.

Another more than 700,000 Ram pickups with similar suspension issues aren't subject to the buyback because of better repair rates, a NHTSA spokesman said.

With 1.56 million recalled Jeeps with rear gas tanks linked to deadly fires, Fiat Chrysler agreed to offer cash to spur owners to visit dealerships for repairs or additional money on top of the value of a vehicle if they decide to trade it in. The company is installing trailer hitches for added protection in lower-speed collisions on the backs of Jeep Grand Cherokee and Liberty SUVs with model years ranging from 1993 to 2007.

Regulators didn't push Fiat Chrysler to repurchase those Jeeps because the trailer-hitch fix has demonstrated safety benefits while repairs to the trucks and SUVs with suspension problems have been deemed ineffective, Mr. Rosekind, the NHTSA chief, said.

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