What Does P0AC8 Mean?
DTC P0AC8 indicates that the 'B' hybrid battery temperature sensor circuit is reading above the maximum expected voltage. For an NTC thermistor circuit, a high voltage typically means the sensor has low resistance (indicating extremely high temperature) or there is a short circuit in the sensor itself. It could also indicate a wiring fault pulling the signal high. The BMS will take protective action, potentially shutting down the hybrid system.
Safety Warning
This code must be taken seriously because it could indicate genuine battery overheating, which is a potential thermal runaway precursor. Even if the fault turns out to be a sensor issue, it must be diagnosed promptly to rule out actual elevated temperatures at the battery module. Follow all high-voltage and thermal safety protocols.
Common Causes
28%
Internally shorted NTC thermistor reading abnormally low resistance
22%
Actual battery overheating at the 'B' sensor location
22%
Short circuit in the sensor signal wire to a voltage source
16%
Corroded connector creating low-resistance path
12%
BMS temperature circuit reference fault
Diagnostic Steps
1
Read the 'B' temperature sensor value on the scan tool. A high circuit condition on an NTC circuit will display as an extremely high temperature. Determine if this could be a genuine overheating event by checking other temperature sensors and battery operating conditions.
2
If other battery temperature sensors read normal, the high reading is likely a sensor or circuit fault. Directly measure the battery module temperature at the 'B' location with an infrared thermometer to confirm.
3
If the module is genuinely hot, investigate the root cause of overheating: check for cell imbalance, excessive charge/discharge rates, or cooling system failure at that location.
4
If the module temperature is normal, disconnect the sensor and measure its resistance. A shorted sensor will read very low resistance (near 0 ohms). Replace the sensor if shorted.
5
Check the signal wire for shorts to voltage sources and inspect the connector for contamination that could create low-resistance paths between pins.
Estimated Repair Cost
$150 - $2,000
Parts + labor, varies by vehicle and location
DTC P0AC8 indicates that the 'B' hybrid battery temperature sensor circuit is reading above the maximum expected voltage. For an NTC thermistor circuit, a high voltage typically means the sensor has low resistance (indicating extremely high temperature) or there is a short circuit in the sensor itse...
The most common cause of P0AC8 (Hybrid Battery Temperature Sensor "B" Circuit High) is: Internally shorted NTC thermistor reading abnormally low resistance
Typical repair costs for P0AC8 range from $150 to $2,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
This code must be taken seriously because it could indicate genuine battery overheating, which is a potential thermal runaway precursor. Even if the fault turns out to be a sensor issue, it must be diagnosed promptly to rule out actual elevated temperatures at the battery module. Follow all high-voltage and thermal safety protocols.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0AC8 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Battery Thermal Management
Difficulty
Type
Generic (SAE)
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