P2D06

Code

Generic P — Powertrain

Motor Electronics Coolant Pump B Overspeed/Air in System

Brand: Generic

Type: P — Powertrain

Views: UK: 33 EN: 44 RU: 38

AI status

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Page language: EN

Causes

Air trapped in the coolant circuit (incomplete bleed)
Faulty or sticking coolant pump (mechanical failure)
Pump controller or motor driver fault in the ECM/PCM
Damaged or shorted pump motor wiring or connector
Incorrect supply voltage or intermittent power to the pump
Faulty pump speed/position sensor or missing/dirty feedback tone ring

Symptoms

MIL / Check Engine Light illuminated
Coolant temperature abnormal (overheat or fluctuating)
Reduced HVAC performance (poor cabin heat) or intermittent heating
Unusual noise from pump (whine, grinding) if mechanical failure present
Coolant leakage or low coolant level if associated with service
Erratic pump operation shown on scan tool (speed not following commanded)

What to check

Read DTCs and freeze-frame data with a scan tool; record drive/operation conditions when fault set
Check for multiple related codes (pump A, temperature sensors, wiring faults)
Visually inspect coolant level, hoses, clamps, and pump for leaks or air entry points
Inspect pump electrical connector for corrosion, bent pins, water intrusion, or loose terminals
Check ground integrity and battery/charging system voltage under load
Monitor pump commanded duty/speed vs actual feedback with a scan tool or oscilloscope

Signal parameters

Supply voltage: nominal vehicle battery voltage (~11–14.5 V) at pump connector during operation
Control input: PWM duty cycle from ECM (0–100%) — pump speed should track commanded duty cycle
Feedback: pump speed sensor or tachometer pulses should produce a stable frequency proportional to RPM
Expected behavior: actual pump speed should follow commanded speed within a tolerance (typically within ±10–20%); sudden spikes indicate overspeed or sensor issues
No excessive electrical noise or missing feedback pulses during steady-state operation

Diagnostic algorithm

Retrieve and record the full DTC list and freeze-frame. Note operating conditions (engine temp, vehicle speed, ambient temp).
Inspect coolant level and top up if low. Perform a proper bleed/air-purge procedure for the coolant circuit. Clear codes and re-run to see if fault returns.
Visually inspect pump, hoses, fittings and connector for damage, coolant ingress, or loose pins. Repair any wiring/connector issues.
With a scan tool, monitor commanded pump duty and actual pump speed/feedback while varying engine/load. Look for mismatch, spikes or missing pulses.
Check supply voltage and ground at pump under operating conditions. Repair any high-resistance connections or poor grounds.
If electrical signals are suspect, use an oscilloscope to inspect PWM control waveform and feedback signal for noise, distortion, or irregular pulses.

Likely causes

Air in the coolant circuit (recent service or low coolant)
Failed pump motor (bearing slip or internal fault)
Open/shorted wiring or poor ground at pump connector
Faulty pump speed feedback sensor or connection
ECM/PCM driver stage fault or software bug

Fault status

⚠️ Status

Fault stored when ECM detects Coolant Pump B running above expected speed or when air in the coolant system causes abnormal pump feedback; MIL may be illuminated. Check hydraulic bleed, pump operation, wiring, and ECM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours