This bulletin announces availability of reprogramming files to optimize the Battery Energy Control Unit (BECU) which is a component part of the HEV battery pack. The new files address the BECU logic used for detection of the HEV battery pack temperature. After the engine is shut off, the battery pack generates a certain amount of self-discharge heat by design. Existing BECU logic uses a threshold for the amount of this heat which is too low. As a result, the Hybrid Motor Assist Regeneration (HEV battery recharge) system and Auto Start Stop features stop operating. In addition to these reprogramming files to address this condition, a design change was made to the replacement battery pack in support of this software update.
