What is OBD-II Code P0B79 – Hybrid/EV Battery Voltage Sense M Circuit Low?
OBD-II Code P0B79 is a standard fault code that appears when there is a problem with the Hybrid or Electric Vehicle (EV) Battery Voltage Sense M Circuit Low. Hybrid and EV vehicles have sophisticated battery systems that require monitoring to ensure that they work properly. The Battery Voltage Sense M Circuit is responsible for monitoring and reporting the battery’s voltage level to the vehicle’s computer system. When the voltage level falls below the specified range, the OBD-II system detects this and sets the P0B79 fault code. This code indicates that there is a problem with the Hybrid or EV battery sensors, and they are showing a low voltage or low signal.
What are the symptoms of OBD-II Code P0B79?
The symptoms of OBD-II Code P0B79 can vary depending on the vehicle make and model, as well as the severity of the issue. The most common symptoms include:
1. Reduced power in the vehicle
2. The engine light will be illuminated on the dashboard
3. The car might fail to start
4. Reduced fuel economy
5. Reduced acceleration
6. A noticeable drop in engine power
What causes OBD-II Code P0B79?
There are several potential causes for OBD-II Code P0B79, including:
1. Damaged or corroded wiring in the HV Battery Voltage Sense M Circuit
2. Faulty battery sensors
3. A faulty battery management system (BMS)
4. A low charge or failing battery
5. A damaged or corroded battery harness
6. Issues with the Hybrid or EV battery pack
How to fix OBD-II Code P0B79?
The first step in fixing OBD-II Code P0B79 is to diagnose the problem correctly. This might include conducting a visual inspection of the battery pack and any related wires, harnesses, or electronics. Next, a diagnostic scan tool will be used to retrieve the fault code and provide data on the battery’s condition. Using this data, the mechanic can diagnose the cause of the fault and take the necessary steps to fix it.
Typically, fixing OBD-II Code P0B79 involves repairing or replacing any damaged wiring or circuits, replacing the battery pack sensors, or replacing the battery management system altogether. In some cases, the battery may need to be replaced entirely if it is too damaged to charge properly.
Once the cause of the fault has been identified and fixed, the mechanic will clear the fault codes using a diagnostic scan tool. Following this, the driver should be able to operate their vehicle as usual.
Can I continue driving with OBD-II Code P0B79?
It is not recommended to continue driving with OBD-II Code P0B79 present. This can lead to further damage to the vehicle’s battery system or other components, and may result in the vehicle being immobilized or unsafe to drive. It is best to take the vehicle to a mechanic as soon as possible for diagnosis and repair.
What are some preventive measures to avoid OBD-II Code P0B79?
To prevent OBD-II Code P0B79 from occurring, it is important to keep up with routine maintenance and inspections of the vehicle’s battery system. Regularly checking the wiring and connections, keeping the battery charged and maintained, and using the appropriate charging equipment can help to prevent issues from arising.
Additionally, following the manufacturer’s recommended service intervals, avoiding heavy acceleration or braking, and maintaining a steady speed can all help to extend the life of the battery and the vehicle overall.
Case Study: OBD-II Code P0B79
A 2016 Toyota Prius was brought to our garage with the vehicle warning light indicating an issue with the Hybrid or Electric Vehicle (EV) Battery Voltage Sense M Circuit Low. Upon scanning the vehicle with an OBD-II scanner, it returned with fault code P0B79. We conducted a thorough visual inspection of the vehicle’s battery system, and it appeared fine. We also used a diagnostic scan tool to retrieve the fault code and provide data on the battery’s condition. With this data, we were able to diagnose the cause of the fault as a faulty battery sensor.
We then proceeded to replace the sensor, and upon testing the vehicle, the warning light was no longer indicating the battery voltage issue. The scan tool was used to clear the fault code, and the vehicle could operate as usual. We advised the owner to keep monitoring the battery system, and conduct routine maintenance to avoid any further issues.
Resources for Further Reading
If you want to learn more about the OBD-II system and fault codes for hybrid and electric vehicles, there are several resources available. Some of the best include:
1. The OBD-II database at www.obd-codes.com, which provides a comprehensive list of codes and detailed explanations of what they mean.
2. The official website of your vehicle manufacturer may also have guides and manuals providing further details on their specific model’s battery system.
3. Online forums such as PriusChat.com, where hybrid and EV owners can connect with one another and share knowledge and tips on maintaining their vehicles.
FAQs
1. What is OBD-II?
OBD-II is the on-board diagnostic system found in modern vehicles. It is used to diagnose and monitor the vehicle’s engine, transmission, and other systems to ensure they are working correctly.
2. What are fault codes?
Fault codes are codes that are generated by the OBD-II system when it detects an issue with a vehicle’s components or systems. These codes provide information to a mechanic or technician to help them diagnose and repair the issue.
3. What is a Hybrid or Electric Vehicle (EV) Battery?
A Hybrid or Electric Vehicle (EV) Battery is a battery pack used in hybrid and electric vehicles to power the electric motor. These battery packs are significantly more complex than traditional car batteries, and require specialized maintenance and inspection to keep them working correctly.
4. What is the Battery Voltage Sense M Circuit?
The Battery Voltage Sense M Circuit is responsible for monitoring and reporting the battery’s voltage level to the vehicle’s computer system. When the voltage level falls below the specified range, the OBD-II system detects this and sets the P0B79 fault code.
5. What are some tips for maintaining a hybrid or electric vehicle battery?
To maintain a hybrid or electric vehicle battery, it is important to follow the manufacturer’s recommended maintenance schedule, keep the battery charged and maintained, conduct routine inspections of the wiring and connections, and follow good driving habits that reduce strain on the battery.