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U0643 Lost Communication With Turbocharger/Supercharger A Temperature Sensor

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

This sensor reports a temperature at charger A, whose exact measuring point the J2012 title leaves open; depending on the design it can watch the compressor outlet or the hot side. GM's tables define charger A as the first one in the exhaust path on series layouts and the bank 1 charger on parallel ones. When the sensor is a digital part, for instance with SENT output, the controller sets U0643 as soon as valid frames stop arriving; analog wiring and range faults go to P2B6E to P2B71 instead, and charger B uses U0689. No manufacturer documents U0643 publicly. Without the temperature the engine management loses a protection input for the charger and usually caps boost, so the engine can feel weak under load.

Likely causes

Wiring near the charger damaged by heat or chafing
Connector loose or corroded
Sensor electronics failed
Engine controller input fault

Symptoms

  • MIL on
  • Reduced boost and power
  • Further boost-related codes stored

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–400
Time0.5–2.5 h

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

Parts involved

turbo a temp sensorvehicle bus wiring

Related codes

U0689P2B6EP2B6FP2B70P2B71U0644

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org, en.wikipedia.org.