LOS ANGELES -- The "check engine" light of the BMW had been glowing for a few days when its owner pulled up to the valet drop-off at Ink, the much-discussed restaurant opened here two years ago by Michael Voltaggio, a "Top Chef" reality show winner.
The driver was greeted for her lunch first by Bruno Cavallini, 32, whose expertise with cars goes far deeper than what is required by his job with the valet parking company at Ink. When Mr. Cavallini asked how she liked the BMW -- something he almost always does with customers who drive performance cars -- she mentioned the warning light.
Mr. Cavallini dug out a hand-held computer code reader from the trunk of his 2004 BMW M3 and plugged it into the diagnostic port of woman's car before driving around to the restaurant's rear lot.
When she returned after lunch, Mr. Cavallini explained the problem: her BMW had a bad coolant sensor, and it should cost about $90, not including labor, to fix.
"And don't pay more than $100 for labor," he told her. She tipped him $20.
The service he provides has not gone unnoticed by the restaurant's owner.
"He is really beyond a valet -- he helps people with their cars, programming the radio, the seat memories and all that," Mr. Voltaggio, himself a serious car enthusiast, said in an interview at the Amelia Island Concours d'Élégance in March.
"We get from 30 to 50 cars a night," Mr. Cavallini said. Estimating that he has probably solved a couple of problems on each shift over the last two years, the total very likely runs to many hundreds by now.
The streak started when he programmed the settings to make the automatic tilt-down feature of a door mirror work for a customer who had not yet cracked the code.
"The next day, someone came in with a Mercedes and couldn't figure out how to set the time on the clock, so I showed them," he said. "Then another guy came in with a Mercedes and didn't know why the check engine light was on."
Mr. Cavallini always brings his laptop computer and a reader for codes in cars' onboard diagnostic system, or OBDII, to his valet job at Ink.
As a teenager, Mr. Cavallini began tinkering with his and friends' cars for fun, mostly BMWs. ("They're easier to work on than Audis," he said.)
"I used to unsolder the Eproms and flash new coding," he said, referring to the process of reprogramming the memory chip in the car's computer. "I didn't find it to be difficult."
His appetite for shop manuals, which he buys online and reads on his laptop, is nearly insatiable. "I like to go in deep and spend hours learning the cars; I'm on my computer studying diagrams," Mr. Cavallini said. "A lot of my friends want their BMWs reprogrammed for European specs, like having the side marker lights always on, just to be different. The factory software, at least up to 2009, is in German; I need to learn German."
Mr. Cavallini also studies technical service bulletins and alerts diners to problems that might require attention.
Sometimes Mr. Cavallini gets tips for his car help. In one case, a customer drove up to the valet drop-off spot at Ink with a flat tire, Mr. Cavallini knew that this particular Audi model had a full-size spare, and he changed the tire in 10 minutes.
"She didn't have any money," he said. "She came back the next day with a $50 tip."
Tire problems are not unusual.
One night, a woman in a Mercedes-Benz pulled up with a flat tire.
"She is crying -- she's late for a screening of a new movie," Mr. Cavallini recalled. So he retrieved the plug kit and air compressor he carries in his car and fixed the leak on the spot, instructing the woman that she needed to get the tire fixed properly the next day.
Another customer pulled up in a BMW with one halogen low-beam headlight burned, concerned that the problem would lead to being pulled over by the police. So he swapped in a bulb from his own car -- no charge.
He looks out for his customers in other ways, too. He checks every car for operating turn signals and brake lights -- and can often fix them right there. Another time, when a couple who came to dinner in their Jaguar sports car had a few drinks, Mr. Cavallini offered to drive them home and take a taxi back to Ink. All three squeezed into the two-seater.
"If a window regulator is broken, I can't fix it there in the parking lot," he said. "But I can pull the glass up so the customer can lock the car or keep rain out."
Mr. Cavallini's helpfulness also reveals an inner curiosity about technically interesting cars. He's tickled by Mercedes and BMW keyless remotes that close all of the windows simultaneously -- information that he loves to share with owners, few of whom have read the manuals for their expensive cars or been briefed by the sales staff.
Mr. Cavallini says he inherited the technician gene from his father, who was a Datsun mechanic in Glendale, Calif.
"My dad taught me the basics -- he knew how to hear if things were right," Mr. Cavallini said.
He remembers rebuilding a lawn mower when he was in elementary school, and by 12 he was changing clutches. He resurrected a dead Honda 600 car from the early 1970s that year, too: "I was excited. It finally started after three months, it had little power or compression, but I drove it."
He attended automotive technical school in Southern California when he was a teenager and passed the Automotive Service Excellence test to become a certified mechanic.
"I've been hearing it forever: 'You should open up a garage,' " Mr. Cavallini said. But he never worked in an auto repair shop. His reason: as someone who loves exotic cars, he has found that owners rarely keep these cars long enough to spend money on them. "It's hard in L.A.," he said. "People want the greatest and latest."
Instead, he enjoys the benefits of being a valet in a city where the entertainment industry assures that expensive cars abound. "I have driven a lot of Porsches, a Carrera GT, Speedsters, replicas," he said. "I drove a Bugatti Veyron as soon as they came out. I've driven an Enzo, a McLaren F1."
His favorite car is a 1960s Mercedes SL roadster. ("It's just the smell of leather, the shifter, the big steering wheel, I like that.") He's driven a Lamborghini Aventador, a Diablo VT and a BMW Z8, but there's one car that's eluded him: "I'm dying to drive a XJ220," he said, referring to a rare Jaguar supercar.
For now, Mr. Cavallini is happy with his calling. "If I could have any job in the world, I would drive cars and find what's wrong with them -- and find them a good home."
Mr. Voltaggio sees the benefit of having someone with Mr. Cavallini's knowledge at the restaurant, relating an anecdote about a top Lamborghini executive who dined at Ink recently: "Michael Lock was here the other night, and Bruno and he were chit-chatting about cars for at least 10 minutes outside. What kind of valet can do that?"
This article originally appeared in The New York Times.