I have a 2012 Civic Hybrid with about 120,000 miles. It recently started having IMA issues. While driving, the dash lit up with all the typical warning lights ( IMA, check engine, brake assist, power steering). Trying to do some research on my own, I could only conclude that my inverter might be bad based on the information I had. I decided to replace the IMA pack which in next to the battery in the backseat. I also checked and charged the 12 volt accessory battery. Initially it seemed successful but soon after the dreaded IMA light was back along with the check engine and the brake light. I thought there might be a reprogramming issue with the IMA system, so I drove it for a couple of weeks to see if it would eventually clear itself. It didn't. It only lead to another complete failure with more lights coming on and the system shutting down. Upon recharging the accessory battery to help move the car from where it was stranded, it all came back to life and ran normally for about 15 or 20 minutes. But then the IMA, check engine and brake assist light all lit back up. I let the car sit overnight and when I drove it the next day, again it ran normally but after 5 minutes or so, IMA light comes back on and no motor assist.
I have kept this information as short and concise as I can but I can fill in more blanks with any other questions. I obviously see that there is a 12 volt issue, because when the accessory battery is fully charged, the car runs normally at first. But I now think there is a rotor/stater issue or sensor issue because of the problem resurfacing when the engine starts to heat up. The most recent check engine codes where P1440 Motor Power Inverter Module Output Circuit Malfunction and P15A5 Motor Current Sensor Circuit Malfunction. Please let me know what other information I can provide, or what I should check to narrow the focus.