The car had been abandoned just metres from Notre Dame, located on the Île de la Cité, by the River Seine.
Reports said that a couple, a man aged 34 and a woman aged 29, were arrested in connection with the case on yesterday on a motorway lay-by near Orange, southern France. They were on their way to Spain.
Both are reportedly known to intelligence services as being "favourable to the ideas of Isis".
The pair were being questioned by French domestic intelligence agents who can hold them for 96 hours without charges under French anti-terror laws.
Police were alerted to the car when a resident rang in to say a vehicle had been poorly parked at 43 rue de la Bûcherie in the 5th arrondissement with its headlights on.
Although unmarked, investigators quickly traced the car to its owner, who Reuters reported is on a French list of potential terror suspects and "has been identified, arrested and placed in custody".
"We think that this person was conducting a test," one police source told Reuters. "The fact that there was no detonating device linked to the gas tanks and that the warning lights were left on are as if they were trying to attract attention."
Bernard Cazeneuve, the Interior Minister, declined to comment specifically on the arrest. But he said praised the "extreme vigilance" of police and intelligence who are working "with an unrivalled intensity" in the context of "an extremely high threat".
"Since the start of the year, we have arrested 260 people, most of them incarcerated, a significant number of whom were preparing attacks that could have led to tragedies," said the minister.
But Florence Berthout, centre-right Mayor of Paris' 5th arrondissement, said she had been informed on Tuesday that the vehicle had "remained stationary for almost two hours" despite being in a zone where parking is "forbidden".
We think that this person was conducting a test
"We have security forces who are tired and who don't have the power of ubiquity. We need to boost the numbers (in such) highly highly-frequented historic districts," she said.
Paris has been high terror alert since the November 13 attacks in which 130 people were killed and French intelligence services have been warning for months about the threat of car bombings.
In May Patrick Calvar, head of France's intelligence service, DGSI, told MPs that he was "convinced" that Isis would "move to the booby-trapped cars stage and explosive devices and that they will move up the scale in this way".
"We risk being confronted with a new form of attack: a terrorist campaign characterised by placing explosive devices in places where large crowds are gathered, and multiplying this type of action to create a climate of panic.
"Once they have bomb makers in place on our soil, they'll be able to avoid sacrificing fighters while creating maximum damage," he said at a parliamentary national defence committee meeting.
Thibault de Montbrial, president of the domestic intelligence think tank, CRSI, said: "A certain number of recent discoveries are considered by analysts to be 'tests' that may prefigure future attacks".
This week, François Molins, the Paris prosecutor, warned that while Isis - which claimed responsibility for the attacks - was losing ground in Syria and Iraq, the threat of terror strikes in Western Europe was ironically "reinforced" as the jihadist group sought to lash out.
One "worrying factor", he told Le Monde, was the threat of the return to France of around 2000 French nationals either on their way to Syria or wishing to return. Some 700-odd are currently in Syria, he estimated.
