Code result
U0639
Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor B
High severity
What it means
The vehicle bus reports loss of communication with smart HV power-electronics coolant temperature sensor B. Inverter/DC-DC cooling switches to a substitute value; derating may follow.
Is it safe to drive?
No — stop driving
This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly.
Most likely causes
Bus wiring open or shorted
highOne of the most commonly reported causes for this code — check this first.
Module without power or ground
mediumA plausible cause — test and verify before replacing parts.
Module failed
mediumA plausible cause — test and verify before replacing parts.
Related help
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