It’s becoming harder and harder for GM execs to claim that the company was largely unaware of the problems with the Chevy Cobalt and other vehicles with an ignition problem that has resulted in at least 13 deaths, dozens of accidents and the long-delayed recall of millions of cars. A new report shows that car rental companies have been telling GM to look into the issue since at least 2005.

Bloomberg News reports that, following a fatal Sept. 2006 crash involving a Cobalt, an investigator for Vanguard Car Rental — then the parent company of rental biggies Alamo and National — wrote to GM urging it to look into the incident.

“[D]ue to the serious nature of this accident we feel that it is imperative that you open a claim and inspect this vehicle for possible defects,” reads the message, uncovered thanks to a Freedom of Information Act request.

Additional documents turned up by Bloomberg show that Enterprise — which purchased Alamo and National from Vanguard in 2007 — pushed GM to investigate a potential Cobalt defect after routine crashes in which the airbags failed to inflate, going back to 2005.

The failure of an airbag to deploy is not definitive evidence that a car’s ignition switch was inadvertently turned to the “off” position, but if the switch is turned off, the airbag will not work as intended in a crash.

According to Bloomberg, Enterprise first pressed GM to investigate following a March 2005 crash in a Saturn Ion — another vehicle involved in the mass ignition recall — that killed the driver and her husband, and resulted in serious injuries to their teen daughter in the back seat.

In July 2005, GM replied to Enterprise that it had inspected the vehicle but didn’t find a defect or malfunction.

Enterprise then asked GM to investigate a fatal Jan. 2006 crash involving a rented Cobalt. The car veered off the road and hit a tree, killing the driver. The car’s airbags did not deploy.

Bloomberg reporters found that GM referred the case to an investigations unit, but could not turn up any documentation showing what occurred after that referral.

An auto industry consultant and former board member at Dollar Thrifty Automotive group likens car rental drivers to canaries in the coal mine for the automotive industry; they’re the first to get their hands on these new cars and, with so many drivers putting so many miles on these cars so quickly, rental cars are usually the first to highlight defects.

“It’s really like a test fleet,” she explains to Bloomberg. “You put a lot of miles on very quick, and any initial defects on the car rise to the surface, and, in fact, that’s the way auto companies were supposed to use this. They were supposed to be able to detect defects very early.”

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