DTC P0A08-264: DC / DC Converter Status Circuit [11/2014 - ]: Description

The DC/DC converter converts the DC 201.6 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 201.6 V into alternating current, and a transformer lowers the voltage. Then, it is rectified and smoothed (into direct current) 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 sends a signal to the DC/DC converter to prohibit its control and receives signals indicating a normal or abnormal condition of the 12 V charging system via the NODD signal line.

If the DC/DC converter malfunctions, the vehicle will become inoperative. Therefore, the power management control ECU monitors the operation of the DC/DC converter and detects malfunctions.

Fig 1: Hybrid Vehicle Converter Wiring Diagram

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DTC No.	INF Code	DTC Detection Condition	Trouble Area
P0A08	264	DC/DC converter malfunction and 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 Frame wire Inverter with converter assembly Fusible link block assembly (MAIN) Fuse (DC/DC-S, IGCT, IGCT NO. 2) Fusible link block assembly (DC/DC) Power management control ECU

RELATED DATA LSIT

DTC No.	INF Code	Data List Item
P0A08	264	+B Inverter Coolant Water Temperature Short Wave Highest Val

HINT:

When the NODD signal line is open, DC/DC converter control is prohibited and the auxiliary battery voltage will be approximately 12 V (or less).
Regarding NODD signal circuit, when the transistor of the power management control ECU turns on, a signal is sent to the inverter to prohibit DC/DC converter control. Sends a malfunction signal to the power management control ECU when the inverter side transistor is on.
If the inverter is overheating, control may be suspended for self-protection of the DC/DC converter and this DTC may be stored.
After repair, clear the DTCs, turn the power switch off and wait for 30 seconds or more and perform the following procedure to confirm that the auxiliary battery low voltage indicated by this DTC has been repaired.
Wait for 2 minutes with park (P) selected, the power switch on (READY) and the following conditions met, then confirm that Data List item "+B" is between 13.0 and 15.0 V.
(If charging is not performed and the electrical load increases, +B voltage may not be steady, and gradually drops.)
1. Headlight switch is in the HI position.
2. A/C blower fan switch is in the HI position.
3. Window defogger switch is turned on.
  If the DC/DC converter has an internal malfunction, DTC P0A08-264 is stored regardless of the auxiliary battery voltage after performing this procedure.
  
  If the auxiliary battery voltage drops, the power switch turns off regardless of DTCs being stored or not.