Following the discovery of an ignition switch problem in certain Cadillac models with standard key ignitions, General Motors is asking dealers to hold off on sales of the cars – mostly used models – until it comes up with a solution. GM issued a “stop-delivery order” on July 8, according to an initial report from Reuters.

The order covers used models of the Cadillac CTS from 2003 through 2013 and Cadillac SRX from 2004 model year through 2006. It excludes 2014 Cadillac CTS models with push-button start and became public after the National Highway Traffic Safety Administration published it as part of an ongoing investigation into GM’s recalls of more than 25 million cars, per a Bloomberg report.

The stop-deliver order includes vehicles that are identifiable with a “D” in the fourth letter of the Vehicle Identification Number. It advises Cadillac drivers to remove items from key rings, including key fobs, and adjust seats and steering columns to ensure sufficient clearance between the driver’s knees and the ignition key.

“If the key ring is carrying added weight and the vehicle goes off road or experiences some other jarring event, or if the driver unintentionally bumps the key ring or items attached to the key ring with their knee, the key may unintentionally move away from the ‘run’ position,” GM’s order reads. “If this occurs, engine power, power steering and power braking maybe affected, increasing the risk of a crash.

“The timing of the key movement out of the ‘run’ position, relative to the activation of the sensing algorithm of the crash event, may result in the airbags not deploying, increasing the potential for occupant injury in certain kinds of crashes.”