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U063A Lost Communication With Hybrid/EV Electronics Coolant Temperature Sensor C

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

Sensor C is the third digitally connected temperature sensor in the cooling loop for the hybrid or EV power electronics. It is found where a system splits the loop further, for example to give a DC/DC converter or onboard charger its own reading. U063A is stored when its frames stop arriving. No public manufacturer documentation names this code or the location of sensor C. California's OBD II rule lists inverter cooling inputs among the monitored parts, so a hybrid has to flag the loss. If only U063A is present while A and B still answer, a local fault at sensor C or its branch of the harness is far more likely than a bus-wide problem. The analog counterparts are P2B24 to P2B27.

Likely causes

Open or chafed wire in the branch that feeds sensor C only
Sensor C connector unplugged after service work or corroded
Sensor C electronics defective

Symptoms

  • Hybrid or EV warning lamp
  • Possible reduction of charging or drive power

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–600
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv electronics coolant temp sensor cvehicle bus wiring

Related codes

U0638U0639P2B24P2B25P2B26P2B27

References: law.cornell.edu, en.wikipedia.org.