DTC P0A08-264: DC / DC Converter Status Circuit [11/2016 - ]: Description

WARNING: This page is about a different car, the 2019 Toyota Highlander, 2018 Toyota Highlander, and 2017 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.

The DC/DC converter converts the DC 288 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 288 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 hybrid vehicle control ECU assembly 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 hybrid vehicle control ECU assembly monitors the operation of the DC/DC converter and detects malfunctions.

Fig 1: DC / DC Converter Status Circuit

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

This DTC is stored when the DC/DC converter circuit has a malfunction or its operation is prohibited by a fail-safe function, or the auxiliary battery voltage drops to 11 V or less with the power switch on (READY). A signal indicating an auxiliary battery malfunction is sent from the DC/DC converter to the hybrid vehicle control ECU assembly via the NODD signal line.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	MIL	Warning Indicate
P0A08-264	DC / DC Converter Status Circuit	The DC/DC converter is malfunctioning (charging has stopped) and the auxiliary battery voltage drops to 11 V or less. (1 trip detection logic)	Wire harness or connector Inverter cooling system Cooling fan system Hybrid vehicle transaxle assembly Rear traction motor with transaxle assembly Inverter with converter assembly Fuse (DC/DC-S) Fusible link block assembly (DC/DC) No. 2 engine room wire Hybrid vehicle control ECU assembly No. 6 floor wire Extension wire assembly	Does not come on	Master Warning Light: Comes on

RELATED DATA LIST

DTC No.	ECU Data List
P0A08-264	+B Inverter Coolant Water Temperature Short Wave Highest Val

If the inverter is overheating, control may be suspended for self-protection of the DC/DC converter and this DTC may be stored.

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 hybrid vehicle control ECU assembly turns on, a signal is sent to the inverter to prohibit DC/DC converter control. Sends a malfunction signal to the hybrid vehicle control ECU assembly when the inverter side transistor is on.