Fault code P0A09 is called “DC/DC Converter Status Circuit Low” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0A09
Fault code P0A09 is intended to be displayed only on hybrid vehicles. Indicates that the Powertrain Control Module (PCM) has detected a low signal in the DC/DC converter status circuit.
The DC/DC converter is designed to convert the DC voltage from the high voltage battery into 12V DC voltage. This is used to supply power to the lights, audio system and vehicle ECU. In addition, the auxiliary battery is charged through the converter.
The control module (PCM) uses the NODD signal line to send commands to the DC/DC converter and receive signals. Indicating the normal or abnormal state of the 12V charging system.
If the vehicle is driven with an inoperative DC/DC converter, the auxiliary battery voltage will drop, preventing the vehicle from continuing to operate. Therefore, the PCM monitors the DC/DC converter and if error P0A09 is present, warns the driver of the detected fault.
Symptoms of vehicle malfunctions
The main signal that an error P0A09 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The control lamp on the control panel will light up (the code will be stored as a fault).
- Other related codes may be present.
- Reduced vehicle performance.
- Increased fuel consumption.
- Deactivation of the electric motor unit.
- Complete failure to start the engine.
The severity of code P0A09 is high, as the fault is related to the main components of the hybrid vehicle. The problem should be eliminated as soon as possible.
Factors that can cause this error code
The error code P0A09 can mean that one or more of the following problems have occurred:
- DC/DC converter is defective.
- Corrosion, loose or broken electrical wiring and connections.
- Blown fuses or fusible links.
- Failure to observe polarity when replacing battery.
- Sometimes faulty PCM module is the cause.
How to fix or reset OBD-2 code P0A09
Some suggested steps for troubleshooting and fix the error code P0A09:
- Connect an OBD-II scanner to the vehicle’s diagnostic connector and read all stored data and error codes.
- Clear the error codes from the computer memory, and test-drive the vehicle to see if the code P0A09 appears again.
- If the error code appears again, visually inspect the electrical wires and connectors.
- If necessary, repair or replace any shorted, broken, damaged, or corroded components.
- Check fuses and fusible links.
- Test the DC/DC converter.
- If the problem persists, check and replace the motor control module (PCM) if necessary.
Diagnose and repair of problems
The first step in the P0A09 troubleshooting process is to review the Technical Service Bulletins (TSB). For known problems with a particular vehicle.
The advanced diagnostic steps are very specific to each vehicle. They may require, special equipment and knowledge to accurately perform the steps.
Visual inspection
Visually inspect the hybrid vehicle’s DC/DC converter and all electrical circuits for signs of corrosion or open contacts. If necessary, remove corrosion and repair defective components.
Check fuses and fusible links that have failed, replace them. After retrieving all stored codes, remove them and test drive the vehicle to make sure code P0A09 has been reset.
If the tests performed do not reveal the problem, the problem may be with the DC/DC converter itself or the PCM module. Therefore, it is better to contact a specialist who can solve the problem with these units.
A common cause of this error is incorrect battery replacement, when the polarity is mixed up during installation. In a simple case, the fuse will blow, in a severe case, the DC/DC converter board.
On which vehicles does this problem occur most frequently
Fault code P0A09 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Ford (Focus, Transit)
- Lexus
- Toyota (Camry, Prius)
Fault code P0A09 can sometimes be found with other errors. The most common are the following: P0098, P0642, P0A08, P0A10, P0A11, P0A12, P0A13, P2229.
