U0638
Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A
U0638 is an OBD-II diagnostic trouble code meaning: Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A. Common causes: open or short circuit in the sensor circuit, malfunction of the temperature sensor itself. Estimated repair cost: $17–78.
Symptoms
- Check Engine light comes on
- The hybrid system may go into emergency mode
- Possible performance degradation
- The cooling system may not work efficiently
- In some cases, components may overheat
Causes
- Open or short circuit in the sensor circuit
- Malfunction of the temperature sensor itself
- Connection problems (oxidized contacts, poor connection)
- Malfunction of the hybrid system control module
- Wiring harness damage
How to Fix
- Check the integrity of the sensor circuit
- Inspect connectors and contacts for damage
- Check sensor resistance according to manufacturer specifications
- If necessary, replace the temperature sensor
- Check and reflash the control module if necessary
Related codes
Error U0638 by Vehicle Brand
FAQ
What does the U0638 code mean?
U0638 is an OBD-II diagnostic trouble code that indicates: Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor A
What causes a U0638 error code?
The most common causes of U0638 include: Open or short circuit in the sensor circuit; Malfunction of the temperature sensor itself; Connection problems (oxidized contacts, poor connection); Malfunction of the hybrid system control module.
How do I fix a U0638 diagnostic trouble code?
To fix U0638: Check the integrity of the sensor circuit. Inspect connectors and contacts for damage. Check sensor resistance according to manufacturer specifications. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with U0638?
Yes, but get it checked soon
How much does it cost to fix U0638?
The estimated repair cost for U0638 is $17–78. Actual cost depends on your vehicle, location, and labor rates.
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