U.S. car safety regulators are investigating electronic gear shifters in more than 850,000 newer model Fiat Chrysler vehicles.
Driver problems with the shifters have caused 121 crashes and 30 injuries.
The shifters are apparently so confusing that drivers have exited the vehicles while they're in gear.
The National Highway Traffic Safety Administration says the shifters' operation is not intuitive and provides poor feedback to the driver.
A few accidents caused by the rollaway vehicles resulted in hospitalizations.
The probe covers 2014 and 2015 Jeep Grand Cherokees and 2012 to 2014 Dodge Charger and Chrysler 300 sedans with 3.6-liter V6 engines.
Fiat Chrysler hasn't issued a recall yet but says it's cooperating with the investigation.