U0638

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

1. Check the integrity of the sensor circuit
2. Inspect connectors and contacts for damage
3. Check sensor resistance according to manufacturer specifications
4. If necessary, replace the temperature sensor
5. Check and reflash the control module if necessary

Related codes

Error U0638 by Vehicle Brand