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DTC codes / P0Exx · Hybrid propulsion / P0E81

P0E81Battery Charger B Temperature Sensor Circuit Range/Performance

P0E81 indicates that the powertrain control module (PCM) has detected an out-of-range or performance fault in the temperature sensor circuit for battery charger B, which is typically the auxiliary charging unit for a high-voltage battery. The PCM compares the sensor signal against expected values and flags the code when the voltage or resistance stays outside the valid window for a calibrated time.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message, often with no other noticeable symptoms.
  • Reduced or disabled charging from the auxiliary battery charger, leading to a slowly draining high-voltage battery.
  • A warning message on the dash indicating a charging system fault or limited electric range.
  • Inconsistent charging performance, such as the charger shutting off early or failing to start.
  • Possible derating of the vehicle's electric drive system if the battery temperature cannot be properly monitored.

Common causes, most likely first

  1. Faulty battery charger B temperature sensor, such as an open or shorted thermistor element.
  2. Damaged or corroded wiring and connectors between the sensor and the PCM, including chafed harnesses or pushed pins.
  3. High resistance or loose ground connection at the charger B housing or sensor return circuit.
  4. Internal fault in the battery charger B assembly that affects the sensor signal, such as a cracked circuit board or failed solder joint.
  5. PCM software calibration issue or internal driver fault causing incorrect sensor readings.
  6. Extreme ambient temperatures or a recently replaced charger that requires a sensor learn or adaptation reset.

How to diagnose and fix it

  1. Use a scan tool to read the live data for battery charger B temperature sensor and compare it with actual ambient and component temperatures to verify the fault.
  2. Visually inspect the sensor, its connector, and the wiring harness for damage, corrosion, or loose pins, and repair any obvious issues.
  3. Measure the sensor resistance with a multimeter and compare it to the manufacturer's specification for the current temperature.
  4. Check the sensor reference voltage and ground circuit integrity by back-probing the connector with a multimeter while the ignition is on.
  5. If the sensor is faulty, replace the temperature sensor or the charger assembly as required by the manufacturer's service procedure.
  6. After repair, clear the diagnostic trouble codes and perform a road test or charging cycle to confirm the code does not return.
  7. If the code persists, check for technical service bulletins or software updates for the PCM that address false temperature sensor codes.

What the charger temperature sensor really does

  • The temperature sensor in battery charger B is often a negative temperature coefficient (NTC) thermistor, so resistance decreases as temperature rises; a faulty sensor can read plausible but incorrect values that still set the code.
  • A common misdiagnosis is replacing the charger assembly when the real problem is a chafed wire in the harness near the charger, which can short to ground only when the vehicle is moving or vibrating.
  • The PCM may set P0E81 if the sensor signal is stuck within a narrow range during a key cycle, even if the sensor is not completely open or shorted, so a simple resistance check at room temperature may not reveal the fault.
  • Extreme cold or heat can cause a marginal sensor to drift out of range temporarily, setting the code without a permanent failure; always check for related codes and freeze-frame data before condemning parts.
  • On some vehicles, the battery charger B temperature sensor shares a reference voltage or ground with other sensors, so a fault in a different sensor on the same circuit can cause P0E81 to set as a secondary code.

Can I keep driving with P0E81?

You can usually continue driving, but avoid relying on the auxiliary charger and monitor the high-voltage battery state of charge closely. If the vehicle enters a reduced power mode or shows a charging system warning, seek service promptly to prevent battery damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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