Yesterday I took my Prius 2012 for a car wash. When the work was done, I started the car but it gave me (for the first time) the check engine light. I got worried and I switched off the car at which point the engine rattled heavily just before it stopped. I got a diagnostics guy to check the issue and the console gave the error: U029A: Lost communication with hybrid Battery Pack Sensor Module. This got me worried and first thing I thought of was checking the battery pack. We managed to get it opened but everything looked intact, there was no sign of anything faulty. My mechanic advised to change the battery controller (which I believe has the sensor) but we couldn't get a replacement. My hunch kept pointing to what could have happened at the car wash, water must have been spilt in a sensitive area. So I asked that we take a look at the wiring at the floor near the driver and co-driver seats. We got the plastic covering these areas off and as expected found water inside two connectors at the right side (driver's side in my country), We sprayed the water out and cleaned them dry and voila, everything worked perfect.
Suspiciously sounds like a wind screen leaking. You can check it by putting the HVAC blower on high recirculate and closing all the doors and windows. This will pressurize the cabin. Then take a mild solution of dish soap and spray it around the exterior of the wind screen. If you have a leak, bubbles will appear at the leak site. Good luck.
Glad you were able to repair the problem. Now you need to find how and where the water go in and repair that.
It resolved itself for me. It was after a day of heavy rain and somehow water had leaked into the spare tire compartment and surrounding area. I dried it out and put a fan back there for a duration of time. It resolved itself after that. Not scientific in any way, but that is what had happened.
i literally googled this code just now to find the answer. my 2012 prius (australian model) come up with the same error code. my error code got triggered while waiting at an intersection while driving. it wasn't raining, the weather was fine. i got it towed to a nearby hybrid mechanic recommended to me by the tow truck driver. after 3 days had past, he called me up told me my car was ready. i went there to pick up my car and the mechanic told me that there is no corrosion, no leakage. bone dry. he checked the terminals on the hybrid battery and harness etc and he couldn't find any problem. all he ended up doing was clean the terminals and that was it. the error code cleared itself. now my car is back to normal.
