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U062F Lost Communication With Coolant Pump C

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

GM assigns coolant pump C to the pump of its low-temperature coolant loop, a separate circuit that runs well below engine temperature. The 2020 table 20OBDG04 fails U062F once LIN communication errors reach three counts, provided the bus itself is not already faulted (U1345), the pump is configured as present and run/crank voltage is at least 11 V. In 2025 (25OBDG04A) the test watches the pump's response frame CWP_Rsp and fails after 2.5 s without it. Both versions are Type B, so the MIL comes on after two trips. If the pump stays silent, the loop loses its circulation and the parts it cools can run hotter. Electric pumps like Bosch's PDE receive their speed command over LIN or PWM and report their own diagnosis.

Likely causes

LIN wire, supply or ground to the low-temperature loop pump damaged
Corroded or loose pump connector
Pump electronics failed
LIN master in the engine controller faulty

Symptoms

  • Check engine light after two trips
  • Parts on the low-temperature loop may run hotter than normal

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–800
Time0.3–2.5 h

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

Parts involved

coolant pump cvehicle bus wiring

Related codes

U0623U0624U0649U0698U0699

References: gsi.ext.gm.com, gsi.ext.gm.com, bosch-mobility.com.