P2D02

Code

Generic P — Powertrain

Motor Electronics Coolant Pump A Underspeed

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 34 RU: 28

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Page language: EN

Causes

Damaged or seized coolant pump (mechanical failure, worn bearings)
Low supply voltage (weak battery, poor charging, high resistance in supply)
Poor ground or corroded/loose connector(s)
Open/shorted wiring or high-resistance connections between pump and controller
Failed pump speed sensor or encoder (incorrect feedback)
Obstruction in coolant circuit (blockage, air lock)

Symptoms

Cooling system warning lamp or message (motor/drive temperature, system cooling fault)
Reduced cooling performance, higher than normal temperatures
Reduced vehicle performance or protection/limp behavior to protect electronics
Unusual pump noise or grinding from pump area
Multiple related DTCs (thermal, battery, or inverter related)
Cabin heater performance changes (increased or reduced heat) on some vehicles

What to check

Read freeze frame and live data with a diagnostic scan tool (pump commanded duty, reported RPM/speed, current draw, supply voltage)
Check battery state of charge and charging system voltage (engine running if applicable)
Visual inspection of pump, harness, connectors for damage, corrosion or overheating
Verify coolant level and inspect for air pockets in cooling circuit
Check continuity and resistance of power and ground circuits to the pump
Measure voltage at the pump connector while the pump is commanded on

Signal parameters

Command input: PWM or duty cycle 0–100% (varies by vehicle)
Measured pump speed: typical electric pump range 0–6000 rpm (vehicle dependent)
Supply voltage at pump: nominal 12–14.5 V on 12V systems (may be higher on high-voltage systems; consult vehicle spec)
Pump current draw: typically up to several amps (commonly 2–15 A depending on pump/powertrain)
Feedback signal type: hall/encoder pulses or tachometer frequency (Hz) reported as RPM by scan tool

Diagnostic algorithm

Retrieve freeze frame and all related codes. Note operating conditions (ambient temp, vehicle mode, battery voltage).
Attempt to re-create the fault by commanding the pump on while monitoring live data: compare commanded duty to measured RPM and current.
Check battery/charging voltage under load. Low system voltage can cause underspeed events.
Visually inspect pump, coolant lines and mounting. Verify coolant level and remove any trapped air from the circuit per manufacturer procedure.
Inspect connectors and wiring for corrosion, damage, loose terminals, or water ingress. Wiggle-test harness while monitoring RPM to detect intermittent faults.
Measure voltage at pump power pin and ground while pump is commanded. A significant voltage drop indicates wiring or connection issue.
Measure pump current draw. Low or zero current with correct voltage suggests an internal pump or driver fault; abnormally high current suggests mechanical binding or blockage.
If pump has a speed/feedback sensor, verify signal quality with an oscilloscope or scan tool (clean square/pulse waveform). Replace sensor if noisy or absent.
If electrical supply and feedback are good but pump speed is low, remove and bench-test the pump (or replace with known good unit) to verify mechanical condition.
If bench test shows pump good, investigate the pump driver/module or control module outputs; check for stored ECU faults and software updates.
After repair, clear codes and perform functional test under the original operating conditions to confirm the fault is resolved.