Tesla has issued its largest voluntary recall to date, affecting 123,000 Model S vehicles due to faulty power steering bolts.

In an email to customers, Tesla advises on 123,000 Model S vehicles built before April 2016 equipped with defective bolts. Made by automotive supplier Bosch, they are known to degrade and loosen over time, which could result in the loss of power steering and the need to use more force to turn the wheel.

“We have observed excessive corrosion in the power steering bolts, though only in very cold climates, particularly those that frequently use calcium or magnesium road salts, rather than sodium chloride,” read a portion of the email.

“Nonetheless, Tesla plans to replace all early Model S power steering bolts in all climates worldwide to account for the possibility that the vehicle may later be used in a highly corrosive environment. If the bolts fail, the driver is still able to steer the car, but increased force is required due to loss or reduction of power assist. This primarily makes the car harder to drive at low speeds and for parallel parking, but does not materially affect control at high speed, where only small steering wheel force is needed.”

No crashes or injuries have been reported.

To remedy the issue, Tesla will apply a retrofit, an hour-long process, shortly after scheduling appointments pending parts availability, with a separate phone number and email address provided for questions.

Other voluntary recalls in the past have been smaller, including an April 2017 53,000-Model S and X recall for faulty parking brakes and an October 2017 second row seating issue on Model Xs due to faulty cables.