Reid Bigland, Chrysler’s U.S. sales chief, said Santander has been a “good partner.” In recent years, lending practices in the subprime auto industry have come under increased scrutiny. Regulators and consumer advocates say it takes advantage of people with nowhere else to turn.

For investors, the allure of subprime car loans is clear: securities composed of such debt can offer yields as high as 5 percent. It might not seem like much, but in a world of ultra-low rates, that’s still more than triple the comparable yield for Treasuries. Of course, the market is still much smaller than the subprime-mortgage market which triggered the credit crisis, making a repeat unlikely. But the question now is whether that premium, which has dwindled as demand soared, is worth it.

“Investors seem to be ignoring the underlying risks,” said Peter Kaplan, a fund manager at Merganser Capital Management.

Worth It?

Asset-backed securities based on auto loans are engineered to keep paying even when some loans sour. Still, some cracks have emerged in the $1.2 trillion market for auto financing. Delinquencies have picked up, as have losses on subprime loans. Auto loan fraud, meantime, is approaching levels seen in mortgages during the bubble.

Auto finance “is not going to bring down the financial system like the mortgage crisis almost did, but it does signal more stress with the consumer,” said Stephen Caprio, a credit strategist at UBS Group AG.

Whatever the case, the Santander-Chrysler relationship has opened a rare window into an industrywide race to the bottom that may have lasting consequences.

In the years after its 2009 bankruptcy, Chrysler looked for a dedicated lender to help customers finance their cars quickly. One reason it picked Santander was the Spanish lender’s expertise in “automated decisioning.” At the time, a Chrysler executive said the process helped Santander “take a little bit more risk and approve more deals because they mine the data” in subprime.

Becoming Chrysler’s preferred lender made sense for Santander. It was aggressively expanding in the U.S. subprime loan market, and Chrysler, the perennial third wheel among the “Big Three,” relied more on buyers with lower credit scores than General Motors Co. or Ford Motor Co.

Problems surfaced almost from the start. Many of them, detailed in the settlement between Santander and authorities in Delaware and Massachusetts, recall some of the excesses of the subprime housing era.