U0634
Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A
U0634 is an OBD-II diagnostic trouble code meaning: Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A. Common causes: coolant temperature sensor malfunction, open or short circuit in the sensor circuit. Estimated repair cost: $56–167.
Symptoms
- Check Engine light comes on
- Hybrid system power reduction
- Battery overheating
- Incorrect coolant temperature readings
- Reduced performance of the hybrid system
Causes
- Coolant temperature sensor malfunction
- Open or short circuit in the sensor circuit
- Poor contact in the sensor connector
- Malfunction of the hybrid system control unit
- Wiring harness damage
How to Fix
- Check the continuity of the temperature sensor circuit
- Check sensor connectors and connections
- Check the functionality of the temperature sensor
- Check the hybrid system control unit
- Repair only from an authorized dealer
Related codes
Error U0634 by Vehicle Brand
FAQ
What does the U0634 code mean?
U0634 is an OBD-II diagnostic trouble code that indicates: Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A
What causes a U0634 error code?
The most common causes of U0634 include: Coolant temperature sensor malfunction; Open or short circuit in the sensor circuit; Poor contact in the sensor connector; Malfunction of the hybrid system control unit.
How do I fix a U0634 diagnostic trouble code?
To fix U0634: Check the continuity of the temperature sensor circuit. Check sensor connectors and connections. Check the functionality of the temperature sensor. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0634?
Do not drive — repair immediately
How much does it cost to fix U0634?
The estimated repair cost for U0634 is $56–167. Actual cost depends on your vehicle, location, and labor rates.
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