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U02BA Lost Communication With Hybrid/EV Electronics Coolant Pump B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Hybrid and electric cars cool their power electronics, such as inverter, DC/DC converter and on-board charger, with electric pumps that hang on a LIN line and report their state to a thermal or vehicle controller. U02BA means pump B of that loop no longer answers. No manufacturer documents U02BA publicly or says which pump bears the letter B. Stellantis shows the layout on the 2024-2025 Dodge Charger and Jeep Wagoneer S: three identical pumps, each with its own software and its own LIN bus to the EVCU; without a master message a pump falls into an emergency mode at full speed and can drain the 12 V battery (STAR S2508000056). GM's 2011 Volt wired pump A directly and rated its circuit fault P0CE9 as Type B. With pump B silent the electronics run hotter and drive power may be cut.

Likely causes

Loose or corroded pump connector, open or shorted LIN wire
Pump power supply or ground missing (fuse, relay, ground point)
Pump electronics failed or pump seized
Pump of another position fitted or controller software outdated

Symptoms

  • Warning for the hybrid/electric drive system, MIL possible
  • Reduced drive or charging power when the electronics warm up
  • Pump running constantly or not at all, 12 V battery drained

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–900
Time0.5–3 h

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

Parts involved

hv electronics coolant pump bvehicle bus wiring

Related codes

U063DU02C1P0CE9U02AE

References: static.nhtsa.gov, gsi.ext.gm.com, bosch-mobility.com, law.cornell.edu.