P0E50

Code

Generic P — Powertrain

Motor Electronics Coolant Pump B Control Circuit Intermittent/Erratic

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 32 RU: 20

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Page language: EN

Causes

Loose, corroded, damaged, or water‑intruded connector at coolant pump B
Broken, chafed, or shorted wiring between ECM and pump (intermittent open/short)
High resistance in supply or ground circuit (poor ground, corroded terminal)
Failed coolant pump motor (intermittent internal brush/commutator or bearings)
Faulty relay or fused power supply feeding the pump
Intermittent ECM driver or internal module fault

Symptoms

Intermittent engine temperature fluctuations or higher-than-normal temperature
Check Engine MIL illuminated (P0E50 stored)
Cooling system noise (pump whining or intermittent operation)
Reduced heater or cabin heat when pump fails intermittently
Possible fault codes related to other cooling components or high engine temp

What to check

Retrieve freeze frame and all stored/related codes before clearing
Check live data for pump command vs actual feedback (if available)
Visually inspect pump harness, connector, and clip for corrosion, damage, or water
Wiggle test harness while monitoring for code set or signal change
Check fuse(s) and any pump relay for proper operation
Measure supply voltage and ground at pump harness with key on/engine running

Signal parameters

Supply voltage at pump power pin: ~Battery voltage (12.0–14.5 V) when running
Control signal: PWM duty cycle 0–100% (vehicle-specific frequency, common 100–1000 Hz)
Expected ground resistance:
Pump motor DC resistance: typically low (ohms range) — compare to OEM spec
Typical running current: often 1–10 A (check OEM spec); large spikes or open circuit indicate fault
No sustained intermittent open/short during commanded operation — waveform should be continuous when commanded

Diagnostic algorithm

Read and record all DTCs and freeze frame data. Note if code is historic or active and if other cooling codes are present.
Clear codes and reproduce the fault by operating vehicle under same conditions (idle, drive, A/C on/off) while monitoring pump behavior.
Visually inspect the coolant pump B connector and harness for corrosion, bent pins, water intrusion, heat damage, or chafed insulation. Repair or replace as needed.
Perform a wiggle test: with scan tool monitoring pump command and status, wiggle the harness from pump to ECM and watch for erratic signals or code set.
Check related fuses and relays for proper function. Substitute known-good relay if suspect.
Measure with a DVOM: battery voltage at pump power pin (key on and engine running), and continuity/voltage drop to ground. Repair high resistance or open circuits.
Measure pump motor resistance with connector disconnected. If open or out of spec, bench-test pump by applying fused direct battery voltage briefly to verify consistent running. Replace pump if intermittent or noisy.
Use a lab scope to inspect the control/PWM waveform on the pump control pin while commanding different duty cycles. Look for noise, dropouts, or unexpected interruptions.
Measure dynamic current draw while pump is running. Excessive or intermittent current spikes indicate motor internal faults or binding.
If wiring and pump test good, check ECM output driver for intermittent faults. Inspect for water, corrosion, or heat at module connectors. If ECM output is erratic and wiring/pump are good, consider module repair/replacement per OEM procedures.
After repairs, clear codes and re-test under the conditions that caused the fault. Document findings and verify no recurrence.

Likely causes

Connector contamination or loose pin at pump harness (most common)
Broken wire that makes intermittent contact when engine/vibration moves
Failed pump motor that runs intermittently under load
Defective ground or fused power feeding the pump
Intermittent output stage in the ECM

Fault status

⚠️ Status

Control module detected intermittent or erratic voltage/current or communication to Coolant Pump B control circuit (sporadic open/short/high resistance or driver error).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours