Powertrain, generic (extended)

P2E79 Hybrid/EV Electronics Coolant Pump C Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P2E79 is the functional verdict on a third pump in the coolant loop of the traction electronics: command and wiring look healthy, yet the pump does not move coolant the way the controller expects. No manufacturer documents P2E79 or says which pump it calls C. GM has published two strategies for its electronics pump: the 2016 ELR sets P0CEA when the spread between power-electronics coolant temperature and charger temperature grows too large once the pump has been on for over 300 s (32 failures in 40, Type B), and the 2019 tables smooth the difference of commanded versus fed-back pump speed (P19FC). A GM patent adds a comparison of measured with expected pump current. Trapped air, blocked passages, a worn impeller or software can be behind it; Stellantis cured a comparable pump B code (P0C74) by a reflash.

Likely causes

Air trapped in the electronics coolant loop after service or a leak
Pump C worn or impeller fouled, delivering too little flow
Kinked hose or clogged cooler passages in the loop
Control software misjudging pump function (update available)

Symptoms

  • Hybrid or EV system warning lamp, possibly MIL
  • Drive power or charging rate limited because electronics run warm
  • Gurgling or whirring noise from the electronics coolant loop

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time0.5–4 h

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

Parts involved

hybrid electronics coolant pump cpower electronics coolant loop

Related codes

P2E7AP2E42P0CEAP2BD7

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, image-ppubs.uspto.gov.