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DTC codes / P0Axx · Hybrid propulsion / P0ACD

P0ACDHybrid/EV Battery Temperature Sensor C Circuit High

P0ACD indicates that the hybrid or electric vehicle battery pack's temperature sensor C circuit is reporting a voltage higher than the manufacturer's expected range, which the battery control module interprets as an open circuit or a short to voltage. The computer has detected an abnormally high signal from this specific sensor, which is used to monitor the temperature of the high-voltage battery for safe charging and discharging.

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

Symptoms you may notice

  • Illumination of the check engine light or a dedicated hybrid system warning light.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • Reduced electric-only range or the vehicle refusing to enter EV mode.
  • A message on the dash indicating the hybrid battery is too hot or too cold, even when ambient conditions are normal.
  • Possible reduced engine power or forced engine operation to protect the battery.
  • In rare cases, the vehicle may fail to start or go into a fail-safe mode that limits speed.

Common causes, most likely first

  1. A faulty temperature sensor C itself, such as an internal open circuit or a short to voltage.
  2. Damaged wiring or a loose connector between sensor C and the battery control module, often due to corrosion or chafing.
  3. A poor ground connection for the sensor circuit, causing a reference voltage to float high.
  4. A malfunctioning battery control module that misreads the sensor signal or supplies an incorrect reference voltage.
  5. Extreme ambient temperatures or a battery pack that is genuinely overheating, though this usually sets a different code.
  6. Aftermarket accessories or improper repairs that have disturbed the sensor wiring harness.

How to diagnose and fix it

  1. Use a scan tool to retrieve all stored codes and freeze-frame data, then clear the code and test-drive to see if it returns immediately.
  2. Visually inspect the sensor C wiring and connector at the battery pack for signs of damage, corrosion, or loose pins.
  3. Measure the resistance of sensor C with a multimeter and compare it to the manufacturer's specification for the current temperature.
  4. Backprobe the sensor signal circuit at the control module connector to check for a high voltage that would indicate an open circuit or short to voltage.
  5. Check the sensor ground circuit for excessive resistance or a poor connection to the battery pack chassis.
  6. If the wiring and sensor test good, substitute a known-good sensor or simulate the signal with a resistor box to see if the code changes.
  7. Replace the faulty sensor or repair the wiring as needed, then clear codes and verify the repair with a test drive.

What a high sensor C reading really means

  • A high voltage on a temperature sensor circuit almost always indicates an open circuit or a short to voltage, not necessarily a failed sensor, so wiring checks come first.
  • The sensor is often part of a harness that runs along the battery pack, and vibration or rodent damage can cause intermittent opens that only set the code under certain conditions.
  • Some vehicles use a single sensor shared between multiple battery modules, so a high reading on sensor C can be caused by a fault in a different module's wiring.
  • Clearing the code without repairing the root cause may lead to a repeat failure and, in some cases, a battery pack that is no longer covered under warranty.
  • A genuine overheating battery can also set a high voltage code if the sensor's resistance curve goes out of range, so always check for cooling system faults before replacing parts.

Can I keep driving with P0ACD?

You can usually drive the vehicle short distances to a repair shop, but avoid aggressive acceleration, heavy loads, and long trips because the battery control module may not be able to accurately monitor battery temperature. If the vehicle enters a reduced-power mode or shows a high-temperature warning, stop driving and have it towed.

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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