U0634

Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor A

Severity

🔴 High

Can you drive?

Do not drive — repair immediately

Approx. repair cost

$56–167 (est.)

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

U0635 U0636 U0637