Miss a payment? Good luck moving that car

The cause was not a mechanical problem — it was her lender.

Ms. Bolender was three days behind on her monthly car payment. Her lender, C.A.G. Acceptance of Mesa, Ariz., remotely activated a device in her car’s dashboard that prevented her car from starting. Before she could get back on the road, she had to pay more than $389, money she did not have that morning in March.

“I felt absolutely helpless,” said Ms. Bolender, a single mother who stopped working to care for her daughter. It was not the only time this happened: Her car was shut down that March, once in April and again in June.

This new technology is bringing auto loans — and Wall Street’s version of Big Brother — into the lives of people with credit scores battered by the financial downturn.