DTC P0A08-264: DC / DC Converter Status Circuit [08/2013 - ]: Description

WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

The DC/DC converter converts the DC 244.8 V of the HV battery into DC 12 V in order to supply power to areas such as the vehicle's lighting, audio, and ECU systems. In addition, it charges the auxiliary battery. A transistor bridge circuit initially converts DC 244.8 V into alternating current, and a transformer lowers its voltage. Then, it is rectified and smoothed (into DC) and converted into DC 12 V. The DC/DC converter controls the output voltage in order to keep a constant voltage at the terminals of the auxiliary battery.

The power management control ECU uses the NODD signal line to transmit a stop command to the DC/DC converter and receive signals indicating the normal or abnormal condition of the 12 V charging system. If the vehicle is being driven with an inoperative DC/DC converter, the voltage of the auxiliary battery will drop, which will prevent the continued operation of the vehicle. Therefore, the power management control ECU monitors the operation of the DC/DC converter and alerts the driver if it detects a malfunction.

Fig 1: DC / DC Converter Status Circuit Diagram

DTC No.	INF Code	DTC Detection Condition	Trouble Area
P0A08	264	DC/DC converter malfunction or the auxiliary battery voltage drops to 11 V or less with the power switch on (READY).	Wire harness or connector Inverter cooling system Hybrid vehicle transaxle assembly Generator cable Motor cable Inverter with converter assembly Fuse (IGCT-MAIN, DC/DC IGCT, DC/DC-S) Fusible link block assembly (DC/DC) No. 3 engine room wire Power management control ECU