The data crash also brought down production at Nissan's factories in Smyrna, Tenn., and Canton, Miss., according to the company.

Nissan spokesman Chris Keeffe did not estimate lost sales or production. Nissan also declined to elaborate on how a power outage at a data center could take down such a mission-critical network and disable the company for several days.

Dealers were surprised the shutdown was so widespread and lengthy. Some told Automotive News they suspected the automaker's linchpin information technology system had been the target of a cyberattack. Keeffe said it was not a cyberattack.

"Our data center in Denver experienced a power failure, disabling our backup systems and prolonging the systems outage," Keeffe said.

He did not say why the power outage also took down the backup systems nor provide details about Nissan's business recovery plan.

Extreme heat in Colorado led to the outages in the Denver area.

Nissan's lengthy recovery period is instructive for automakers.

Businesses should have backups of their data, applications and systems in different places across the country, said Armistead Whitney, CEO of Apptega, an Atlanta company that helps companies manage IT risks.

"That way, when one facility, area or region experiences a major disruption, the chances are extremely low that another geography is impacted, resulting in the disruption only lasting minutes or a couple of hours instead of days," Whitney said.

The consultant advises against co-locating communication systems such as phones and email with core business applications.

"When a major business system goes down, it also brings down the communications system, which compounds the outrage of the outage by not being able to provide timely updates to colleagues and customers."

Nissan's disruption should have been anticipated, said Ray Brandt, CEO of Ray Brandt Automotive Group in suburban New Orleans.

"We were surprised that it happened without a real backup plan to make sure that if it did happen, we could minimize the pain," Brandt said. "I'm surprised it took four days to get it resolved."

During the NNANet shutdown, Nissan and Infiniti stores were unable to order new vehicles from Nissan, report vehicles that have been sold, place online part orders or process warranty claims.

Customers complained on social media about being unable to get recall information, having service appointments rescheduled and, for one customer, being unable to have an ignition key reprogrammed.