P0AFC Hybrid Battery Pack Sensor Module
OBD-II Trouble Code Technical Description
Hybrid Battery Pack Sensor Module
What does that mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Toyota, Honda, Ford, Subaru, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
If your OBD II equipped, hybrid vehicle (HV) has stored a code P0AFC, it means that the powertrain control module (PCM) has detected a malfunction in the hybrid battery pack sensor module. The hybrid battery pack sensor module is more commonly referred to as the hybrid vehicle battery control module (HVBCM). This code should be exhibited only in hybrid vehicles.
The primary responsibility of the HVBCM (which interacts with the PCM and other controllers) is to monitor and control the the high-voltage battery pack. Twenty-eight (nickel metal-hydride) batteries, configured of eight separate 1.2-volt cells – arranged in series, make up the HV battery pack. The high voltage hybrid battery packs are wired in series with busbar connectors and sections of high voltage copper cable.
Battery temperature, individual cell resistance, battery charge levels, and overall battery pack condition are included among the functions monitored and calculated by the HVBMS.
The HVBMS receives input data from each individual cell in order to monitor individual battery/cell temperature and resistance levels in the battery pack. This information is used to regulate battery charge rates and operate battery cooling fans (among other things). Each individual cell (or battery, depending upon the type of system) is outfitted with an integrated ammeter/temperature sensor.
If the HVBMS provides the PCM with an input signal that indicates a HVBCM (hybrid battery pack sensor module) malfunction has occurred, a code P0AFC will be stored and a malfunction indicator lamp may be illuminated. Most vehicle applications will require multiple failure cycles prior to MIL illumination.
A typical hybrid battery pack:
What is the severity of this DTC?
Hybrid battery pack sensor module/HVBCM failure (and a stored code P0AFC) could result in deactivation of the electric propulsion system. The P0AFC should be addressed with urgency.
What are some of the symptoms of the code?
Symptoms of a P0AFC trouble code may include:
What are some of the common causes of the code?
Causes for this code may include:
What are some P0AFC troubleshooting steps?
The high-voltage battery system should only be serviced by qualified personnel.
Access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of HV battery system diagnostic information will be necessary before attempting to diagnose a code P0AFC.
I like to begin my diagnosis with a visual inspection of the HV battery pack and all controller area network (CAN) harnesses. I would focus on signs of corrosion, damage, or other obviously open circuits. Remove corrosion and repair (or replace) defective circuitry as required. Before performing any battery load testing, make sure that there are no corrosion issues present on the battery pack, that all connections are secure, and that the battery pack is fully charged.
Proceed by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and pertinent freeze frame data. Record this information before clearing the codes and test driving the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode (no codes stored) at this point; the code is intermittent and may be much more difficult to diagnose.
You may suspect a defective HVBCM/PCM or a controller programming error if all controller power (input) and ground circuits are intact and there is no sensor power (output) supply voltage from the HVBCM/PCM. Controller replacement will require reprogramming.
If there is no HVBCM supply voltage present, test all related controller power supply fuses and relays. Replace defective components as required.
Any controller that shows signs of water, heat, or collision damage should be considered defective.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0afc in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0afc and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0afc.
