On Saturday, the newly joined Fiat Chrysler group filed a 5,600-car recall with the National Highway Traffic Safety Administration (NHTSA) to recall all 2013 through 2015 model year Fiat 500e Electric Cars to fix a problem with ‘incompatible software’ between the car’s electric vehicle control unit and battery pack control module.
As the Detroit News reports, the fault lies in communication problems between the two modules in the event of a ‘limp home’ event: a fault or state of battery charge low enough to cause the car to limit power to its drivetrain in order to prevent complete shutdown.
In affected cars, entering that mode causes the two modules to miscommunicate, causing a complete car shutdown and total loss of power. In the words of Fiat Chrysler, “if the vehicle goes in to limp home mode, incompatible software between Electric Vehicle Control Unit and Battery Pack Control Module may cause the electric system to fully shut down.”
The fault itself, which affects all cars built between March 2012 and November 1 2014, stems from an software update Fiat Chrysler issued in March 2014. That software update was designed to improve charging system operation, on-board diagnostics and range estimation of the Fiat 500e, and introduced Limp Home Mode as part of continued improvements to the vehicle’s on-board battery management system.
The problem only became apparent when it was noticed that the EVCM did not understand or recognize the existence of the limp home mode when it was triggered, causing the EVCM to experience an error condition and shut down.
The software update — issued as part of a previous voluntary recall on all cars made before March 2014– reprogrammed the EVCU and BPCM units of cars already made with the latest ‘production calibration’ software. Cars made after March 2014 and before November 2014 were programed with that same software in the factory. Thus, all Fiat 500es made between 2012 and 2014 became affected by the issue.
Since Fiat Chrysler noticed and fixed the fault in a new version of the operating software — which it begun to program into production vehicles on November 1 — all cars made after November 1 last year are not affected.
Last May the Fiat 500e minicar, was recalled to fix a fault in its high-voltage inverter system that could owners stranded at the side of the road with no power in the event of failure. In addition to an earlier recall for a minor fault, this is the third time Fiat Chrysler has recalled the Fiat 500e compliance car.
Fiat Chrysler will be contacting owners of affected Fiat 500es in the near future, with dealers offering free updates under warranty. In the meantime, concerned owners can call Fiat Chrysler in the U.S. on 1-888-242-6342, or find out more information on the recall at the SaferCar.Gov website.
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