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U02AE Lost Communication With Hybrid/EV Battery Coolant Pump

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The battery coolant pump circulates coolant through the high-voltage pack. Electrically commutated pumps like Bosch's PAD2 carry their own electronics, take a speed request by PWM or LIN and report back. U02AE applies when such a pump is a bus node and stops answering the controller that runs battery thermal management. No manufacturer documents U02AE publicly. Pumps driven over a plain control line report P0C47 and its siblings instead: GM's 2019 hybrid table checks the HV battery pump line for under 200 mA or over 3 A while on, Type B. Under CARB 1968.2, every electronic input and output used to heat or cool the high-voltage battery must be monitored. Without the pump the pack warms faster, so charge and drive power may be limited. U0694 and U0695 name pumps A and B.

Likely causes

Moisture or corrosion in the pump connector, pushed-out terminal
Pump electronics failed (seized rotor, internal fault)
LIN/bus wire, supply fuse or ground of the pump interrupted
Software fault in the battery or thermal management controller

Symptoms

  • Hybrid or battery warning, possibly with the MIL
  • Reduced charging rate or electric drive power, especially when hot
  • Battery temperature rises faster than usual

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–900
Time0.5–3 h

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

Parts involved

hv battery coolant pumpvehicle bus wiring

Related codes

U0694U0695P0C47U02BAU02AB

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