P2E46

Code

Generic P — Powertrain

Hybrid/EV Electronics Coolant Pump B Overspeed - Dry Run

Brand: Generic

Type: P — Powertrain

Views: UK: 17 EN: 79 RU: 21

AI status

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Page language: EN

Causes

Air trapped in the coolant circuit (partial or complete dry running)
Low coolant level or empty reservoir
Mechanical failure inside the pump (worn bearings, damaged impeller) reducing load
Pump motor driver or inverter malfunction providing incorrect frequency/voltage
Faulty pump speed sensor or feedback wiring (false high RPM reading)
Short/open in supply/ground or intermittent connector causing erratic control

Symptoms

Malfunction Indicator Lamp (MIL) or hybrid system warning illuminated
Stored or pending P2E46 in the hybrid/vehicle control module
Unusual high-pitched whine or noisy pump operation
Reduced HVAC or battery thermal control performance
Coolant temperature abnormalities (overheat or unstable readings)
Possible visible coolant leaks or low reservoir level

What to check

Follow high-voltage safety procedures and isolate the HV system before service or testing.
Read and record all stored/related DTCs and freeze-frame data with a capable scan tool.
Visually inspect coolant reservoir, hoses, radiator, and pump for leaks, damage, or low level.
Inspect electrical connectors and wiring to Pump B and its motor controller for corrosion, looseness, or damage.
Capture live data: pump commanded speed, actual pump speed (RPM or Hz), pump supply voltage, and motor current.
Compare commanded vs actual speed and look for significant discrepancy or actual RPM above published max.

Signal parameters

Pump commanded speed (duty %, Hz or commanded RPM) — value requested by controller
Pump actual speed (RPM or Hz) — feedback from pump speed sensor
Supply voltage to pump motor (V) — should be within vehicle spec when commanded
Motor current draw (A) — low current may indicate dry run or no load; high current may indicate binding
Coolant temperature (°C/°F) — sensor upstream/downstream of pump
Coolant level / reservoir reading — proper fill level required

Diagnostic algorithm

Safety first: isolate high-voltage system per manufacturer procedures before any physical work.
Read DTCs and freeze-frame; note any related codes (pump A, battery pump, thermal system) and live data.
Perform basic visual inspection: coolant level, leaks, hose collapse, reservoir cap, and pump housing.
Check connectors and wiring to Pump B and motor controller for corrosion, bent pins, damaged insulation, or poor grounds.
With the vehicle in a safe diagnostic mode and HV isolated as required, power the pump under scan-tool control and record commanded vs actual speed, supply voltage and motor current.
If actual RPM is high while current is very low, suspect dry run/air in system or internal pump geometry failure; confirm coolant level and bleed the system according to procedure.
If actual RPM reading is implausibly high but mechanical noise and flow suggest normal operation, verify speed sensor and feedback wiring (check resistance/continuity and scope signal where available).
If motor controller is providing excessive frequency/voltage, test controller output signals and supply voltages; swap with a known-good controller if applicable/allowed by manufacturer.
If pump mechanical failure is suspected (no load, unusual noise, metal debris in coolant), remove and bench-test or replace pump assembly and clean coolant circuit; inspect impeller and bearings.
After corrective actions, clear codes, recharge and bleed coolant, then run system under various loads to verify proper commanded vs actual speeds and that DTC does not return.
If fault persists, consult OEM diagnostic information, re-flash/update controller software if available, or escalate to specialist repair.

Likely causes

Air in the system (most common when flagged as dry run + overspeed)
Low coolant level or leaked/evaporated coolant
Internal pump mechanical failure (reduced hydraulic load allowing overspeed)
Pump motor controller/inverter failure (delivering excessive frequency/voltage)
Speed/position sensor or harness fault reporting incorrect RPM

Fault status

⚠️ Status

Hybrid/EV Coolant Pump B overspeed detected (dry run suspected). Pump running at excessive speed likely due to insufficient coolant load, pump or driver fault. Service required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 2.0-4.0 hours