All eyes on Friday's JPMorgan earnings data

It's been a scandal-filled few months for banks.

JPMorgan Chase revealed a trading loss of at least $2 billion, triggering an investigation by the government and hearings in Congress. Then the large banks were implicated in a global dust-up over interest rate manipulation.

All this happened amid signs of a slowdown in the U.S. and Chinese economies and a debt crisis in Europe, which won't help the banks as they report their financial results for April through June.

All eyes will be on JPMorgan on Friday, when it becomes the first bank to report. The trading loss rattled the company's stock price and hurt both its reputation and that of chief executive Jamie Dimon, who is expected to provide an update.

Analysts aren't expected to give the company a pass. "We expect a detailed account of what went wrong, what has changed and what is remaining," says Jason Goldberg, a bank analyst at Barclays Capital, a global investment bank.

Goldberg, like most investors and analysts, has no idea how deep JPMorgan's loss is. He said it could range from $2 billion to $9 billion. JPMorgan has said it lost the money trying to hedge against risk.

JPMorgan's stock has fallen from $40.74 before disclosing the trading loss May 10 to $34.04 on Thursday.

Other bank stocks have also been dragged down because of uncertainty in Europe, the recession that has gripped some countries there and economic slowdowns in China and India.

Those worries have led to fewer corporate deals, which provide much-needed fees for the big banks.