What Does P0AC7 Mean?
DTC P0AC7 indicates that the 'B' hybrid battery temperature sensor circuit is reading below the minimum expected voltage. For an NTC thermistor, a low voltage corresponds to very high resistance (very cold reading) or an open circuit condition. Alternatively, the signal wire itself may be shorted to ground. The BMS will use default or substitute temperature values, potentially limiting charging and discharging rates.
Common Causes
30%
Short to ground in the temperature sensor signal wire
26%
Open or failed NTC thermistor (reading as very high resistance)
22%
Disconnected sensor connector inside the battery enclosure
13%
Water intrusion causing ground path in the connector
9%
BMS temperature input pull-up resistor or circuit fault
Diagnostic Steps
1
Read the 'B' temperature sensor value on the scan tool. Depending on the circuit design, a low circuit condition may display as an extremely cold temperature (e.g., -40°F) or a minimum-scale value.
2
Disconnect the temperature sensor and check if the scan tool reading changes. If the reading goes high (hot) with the sensor disconnected, the sensor or its wiring was causing the low condition. If it stays low, the fault is in the BMS or between the connector and the BMS.
3
Measure the sensor resistance. For an NTC thermistor at room temperature, it should read within the specified range (typically 10k-47k ohms). An OL reading indicates an open sensor.
4
Check for shorts to ground in the signal wire by measuring resistance from the signal pin to chassis ground with the sensor disconnected. Any low resistance reading indicates a ground fault.
5
Inspect the battery enclosure for moisture intrusion that could create leakage paths to ground.
Estimated Repair Cost
$120 - $600
Parts + labor, varies by vehicle and location
DTC P0AC7 indicates that the 'B' hybrid battery temperature sensor circuit is reading below the minimum expected voltage. For an NTC thermistor, a low voltage corresponds to very high resistance (very cold reading) or an open circuit condition. Alternatively, the signal wire itself may be shorted to...
The most common cause of P0AC7 (Hybrid Battery Temperature Sensor "B" Circuit Low) is: Short to ground in the temperature sensor signal wire
Typical repair costs for P0AC7 range from $120 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of a direct battery temperature sensor creates a blind spot in thermal monitoring. The BMS may over-restrict battery usage as a precaution, or if it defaults to an assumed temperature, it may not detect actual overheating at the 'B' sensor location.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0AC7 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Battery Thermal Management
Difficulty
Type
Generic (SAE)
Recommended Tools
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