Technical Description of OBD-II Trouble Code
Replace the Hybrid Battery Pack
What does that signify?
This generic powertrain diagnostic trouble code (DTC) commonly applies to numerous OBD-II hybrid electric vehicles. This may include vehicles from Toyota (Prius, Camry), Lexus, Fisker, Ford, Hyundai, GM, etc.
When a code P0A80 is stored, it indicates that the powertrain control module has detected a malfunction in the hybrid vehicle battery management system (HVBMS). This code signifies that a weak cell failure has occurred in the hybrid battery pack.
Hybrid vehicles (which do not require external charging) utilize nickel metal-hydride battery packs. Battery packs are essentially blocks of batteries (modules) that are connected using sections of busbar connectors or cables. The typical HV battery consists of eight (1.2-volt) cells in series. The typical HV battery pack is composed of twenty-eight modules.
The HVBMS regulates the charging level of the battery pack and monitors its state. The HVBMS and PCM consider individual cell resistance, battery voltage, and battery temperature when determining battery pack condition and the desired charging level.
Multiple ammeter sensors and temperature sensors are strategically placed throughout the HV battery pack. In most cases, each cell is equipped with an ammeter/temperature sensor. These sensors provide the HVBMS with data from each cell. The HVBMS compares individual voltage signals to identify any inconsistencies and reacts accordingly. The HVBMS also provides the PCM with data, via the controller area network (CAN), regarding battery charge level and battery pack condition.
When the HVBMS provides the PCM with an input signal reflecting inconsistent battery or cell temperature and/or voltage (resistance), a code P0A80 will be stored and a malfunction indicator lamp may illuminate.
Example location of a hybrid battery pack, in a Toyota Prius:
What is the severity of this DTC?
A code P0A80 indicates a serious malfunction in a major component of the hybrid powered vehicle. It should be addressed as an urgent matter.
What are some of the symptoms of the code?
Symptoms of a P0A80 trouble code may include:
What are some of the common causes of the code?
Causes for this code may include:
What are some P0A80 troubleshooting steps?
NOTE: The high voltage battery pack should only be serviced by qualified personnel.
If the HV in question has more than 100,000 miles on the odometer, suspect HV battery pack failure.
If the vehicle has less than 100K miles, a loose or corroded connection is likely the source of the malfunction. HV battery pack repair or remanufacture is a possibility, but these options may prove unreliable. The safest method to rectify a defective HV battery pack is replacement with a factory part. If this is cost prohibitive, consider a used HV battery pack.
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of HV battery diagnostic information will be needed to diagnose a code P0A80. Use the scanner to observe HV battery charging data after obtaining testing procedures and specifications from the HV information source. Component location diagrams, wiring diagrams, connector face views, and connector pin out charts will be instrumental in reaching an accurate diagnosis.
Visually inspect the HV battery pack and all circuitry for signs of corrosion or open circuits. Remove corrosion and repair defective components as required.
After retrieving all stored codes and pertinent freeze frame data (connect the scanner to the vehicle diagnostic port), clear the codes and test drive the vehicle to see if the P0A80 is reset. Test drive the vehicle until the PCM either enters readiness mode or the code is reset. If the code is reset, use the scanner to identify the HV battery cells that are experiencing inconsistencies. Make a note of the cells and continue with your diagnosis.
Using freeze frame data (from the scanner), determine whether the condition that caused the P0A80 to be stored involved an open circuit, high cell/circuit resistance, or an HV battery pack temperature discrepancy. Test appropriate HVBMS sensors (temperature and voltage) by following manufacturer testing specifications and procedures. Replace sensors that do not comply with the manufacturer’s specs.
You may test individual cells for resistance using the DVOM. If the individual cells exhibit an acceptable degree of resistance, use the DVOM to test resistance in busbar connectors and cables. Individual cells and batteries may be replaced, but total HV battery pack replacement may prove to be the most reliable fix.
