BMW North America is conducting a new safety recall on certain M cars, from the 2015-2017MY, which is related to a previous service campaign.

According to the National Highway Traffic Safety Administration (NHTSA), the automaker’s dealers have apparently messed up a repair and used the same rear sub-frame bolts to replace the rear differential, instead of using new ones.

The bolts are specified as a one-time-use fastener during the vehicle assembly process, and if these have been reused, then “it is possible that the clamp force may not be achieved when torqueing down the bolts, and therefore, they could loosen over time.” In extreme cases, the cars’ handling and control can be affected, increasing the risk of a crash.

BMW’s dealers cannot be blamed, however, because the repair instructions did not inform them to use new rear sub-frame bolts, as the feds write in the description of the cause.

As for the number of potentially involved vehicles, it adds up to 66 and counts five M2 Coupes, made from May 31 to June 20, 2016, 32 M3 Sedans produced from June 17, 2014, throughout June 13, 2016, 26 M4 Coupes assembled between May 2, 2014, and June 14, 2016, and 3 M4 Convertibles, put together from May 29, 2015, to May 27, 2016.

BMW is not aware of any accidents or injuries related to this condition. The recall is expected to begin on October 24 and will see technicians replace the rear sub-frame bolts with new ones, free of charge.

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