P2C72

Code

Generic P — Powertrain

Hybrid/EV Electronics Cooling System Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 14 EN: 34 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Low or contaminated coolant
Coolant leak (hoses, fittings, radiator, heat exchanger)
Coolant pump failure (mechanical or electrical)
Clogged radiator, heat exchanger, or coolant passages
Thermostat or flow-control valve stuck/failed
Radiator or condenser fan failure or airflow restriction

Symptoms

Hybrid/EV cooling system warning or fault indicator
Reduced propulsion power, derate or limp-home mode
Elevated inverter/DC–DC temperature readouts or rapid temperature rise
Cooling fan(s) running constantly or not running when commanded
Visible coolant leak, damp spots or coolant odor
Poor climate control performance (in some systems)

What to check

Retrieve DTCs and freeze-frame with a capable scan tool; record related codes and live data
Visual inspection for coolant leaks, hose condition, clamps and signs of contamination
Check coolant level and condition in the service reservoir (when safe to do so)
Inspect radiator/heat exchanger and airflow path for obstructions or damage
Operate vehicle to reproduce condition while monitoring inverter/battery coolant temps, pump command and fan status
Verify fan operation and electrical supply to pump and fan(s)

Signal parameters

Inverter/power-electronics coolant temperature (°C) — monitor inlet and outlet temps and delta
Commanded pump duty or relay status (%) and actual pump current draw (A)
Radiator fan commanded state vs actual RPM or percent
Coolant system pressure (kPa) during pressure test and operating condition
Flow sensor frequency or flow indication (if equipped)
Ambient air temperature and vehicle load at time of test

Diagnostic algorithm

Connect a capable scan tool and read all manufacturer and hybrid/EV specific codes; save freeze-frame and live data.
Perform a thorough visual inspection: check coolant level, condition, hoses, clamps, heat exchanger, wiring and connectors for obvious faults or leaks.
If coolant is low, top to correct level following safe procedures and inspect for leaks. Do not open a hot high-voltage cooling system without proper precautions.
Pressure-test the coolant system to locate external leaks; repair any leaks found and re-test.
With a technician-safe procedure for the high-voltage system, run the vehicle to normal operating conditions while monitoring inlet/outlet coolant temperatures, pump command and current, fan command and speed, and any flow-sensor outputs.
If pump commanded but not operating, check fuses, relays, power supply and ground. Measure pump current; replace pump if electric motor is not drawing expected current or is seized.
If temperatures rise with pump operating, inspect radiator/heat exchanger for blockage or internal restriction and verify thermostat/flow valve operation; clean or replace as needed.
Test coolant temperature sensors and associated circuits for correct resistance/voltage and replace faulty sensors. Repair wiring/connectors as required.
After repairs, bleed air from system per manufacturer procedure, clear codes, and perform a road/operational test while monitoring temperatures and signals to confirm normal performance.
If system still fails to meet performance targets, consider control module/software faults and consult manufacturer service information for advanced diagnostics or module replacement.

Likely causes

Low coolant level or air trapped in system
Coolant pump electrical failure or seized pump
Blocked radiator/heat exchanger reducing flow
Radiator fan(s) not operating or reduced airflow
Faulty coolant temperature sensor or incorrect sensor reading

Fault status

⚠️ Status

Hybrid/EV cooling system performance fault stored. The system may trigger a warning lamp and, depending on severity, reduce power or enter protective mode. Freeze-frame and related live data are available for diagnostic use.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4 hours