A few days ago the EPS (electric power steering) went out while my wife was driving. She managed to park, and when I picked her up the EPS was working again. She said the "EPS" light came on before the failure. Took the car to the dealership, but they couldn't pull any codes (everything was working), and I had no problems. The next day my daughter was driving and everything went out (or so she said). She pulled over, and the car would not start. I had no problem jump-starting the car. I could start it again once we got home, but the next morning it was dead: typical starter relay sound from behind the glove compartment.

I'm replacing the starter battery, but I'm worried that there is something else radically wrong. Here's why: this is a hybrid, and even if the 'starter' battery is completely dead, everything (including and especially the EPS) should run fine off the main (IMS) battery, even if the gas engine shuts off, as it does with autostop. I had plenty of bars on the charge indicator.

I wonder if it isn't the ignition switch. For a couple of weeks before the first EPS failure, when I turned the key to start there was nothing. The second time it started right away. This could be an indication of a failing starter battery, but it does not explain the failure of the EPS while the car was under power and using the IMS battery source. Note: the IMS battery pack was replaced--brand new-- at about 78,000 miles; the car now has about 125,000. If the IMS battery were failing, this should have shown up when the technicians pulled the codes.

I should note that the problem has never occurred while I've been driving, so I can't give any clearer idea of the sequence. But I'd appreciate any input, because these intermittent problems are so hard to diagnose.