Powertrain, generic (extended)

P2E46 Hybrid/EV Electronics Coolant Pump B Overspeed - Dry Run

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2E46 is the dry-run report of electronics coolant pump B: faster than commanded at lower current, the signature of air at the impeller. Porsche describes such self-monitoring on the traction-battery pump of the 2018 Panamera plug-in hybrid (code P0C4A00 there). On Mercedes 167-series SUVs with the M177 V8 and 48 V, trapped air forces the 15 W low-temperature pump into a protective dry-run state and sets pump A's P2B2A7A with a yellow coolant warning; Mercedes prescribes vacuum filling and repeated venting. For BAE hybrid buses the pump maker EMP warned that filling with the pump at only 20 % speed leaves air at the inlet and ruins the shaft seals. No manufacturer publicly documents P2E46. Bleed the loop and find the leak first. Plain overspeed is P2E48, pump A's dry-run code P2B2A.

Likely causes

Low coolant level from a leaking hose, joint or component
Air left in the loop after service without vacuum fill
Pump B damaged by earlier dry running

Symptoms

  • Coolant warning message and MIL
  • Pump starts briefly, then stops again
  • Gurgling noise or falling level in the electronics reservoir

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–800
Time0.5–3 h

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

Parts involved

hybrid electronics coolant pump bpower electronics coolant loop

Related codes

P2E48P2E47P2E49P2B2AP2D06

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.