P2B29

Code

Generic P — Powertrain

Hybrid/EV Battery Pack Coolant Pump A Overspeed - Dry Run

Brand: Generic

Type: P — Powertrain

Views: UK: 26 EN: 111 RU: 25

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Low coolant level or air trapped in the battery cooling loop (dry-run condition)
Blocked or restricted coolant flow downstream (closed valve, collapsed hose, debris)
Failed or damaged pump (worn bearings, broken impeller) causing abnormal speed behavior
Faulty pump speed sensor or missing/erroneous speed feedback signal
Faulty pump motor driver or controller (incorrect PWM or stuck-high command)
Wiring harness damage, poor connector, high resistance or intermittent circuits

Malfunction Indicator Lamp (MIL) or warning message related to battery cooling
High or rising battery pack temperature or reduced thermal management performance
Unusual high-pitched or whining pump noise (overspeed)
Visible coolant leak or low coolant level in reservoir
Loss of charge/heavy-load performance, possible limp-home behavior
Stored DTC P2B29 and possibly related codes

Read stored/ pending DTCs and freeze frame data with a capable scan tool; note pump speed, commanded duty, battery temp and vehicle conditions when DTC set
Visually inspect coolant reservoir level, hoses, fittings, and pump area for leaks, collapsed hoses, or kinks
Check for air in system; verify bleed procedure was performed if recently serviced
Verify presence and condition of connectors and wiring to the pump and pump controller; look for corrosion, loose pins or heat damage
Monitor live PIDs: commanded pump speed/PWM duty, actual pump RPM or frequency, motor current/amps, pump supply voltage
Compare actual pump speed to commanded speed across range (idle, commanded low and high) using scan tool or oscilloscope

Expected pump RPM: typically within commanded range ± tolerance (manufacturer-specific). Overspeed defined as RPM significantly above commanded value
Command signal: PWM duty cycle or voltage command from thermal management module (0–100% duty typical)
Feedback signal: tachometer/frequency or hall-sensor pulses indicating actual RPM
Motor current draw: rises with load; very low current with high RPM suggests dry-run or loss of hydraulic load
Supply voltage: stable high-voltage supply per vehicle spec during operation

Capture codes and freeze frame with scan tool. Record battery pack temp, vehicle speed, SOC, and conditions when fault occurred.
Perform visual inspection of coolant level, reservoir cap, hoses, fittings, and pump for leaks, damage or signs of air.
Verify the cooling system is properly bled. If low coolant or air is found, refill and bleed per service procedure, then clear codes and retest.
With appropriate safety/isolation for HV systems, monitor live data: commanded pump duty, actual RPM, motor current and supply voltage while requesting pump operation via scan tool.
If actual RPM is higher than commanded or RPM is present with no load/zero duty, check speed-sensor signal integrity (voltage waveform or frequency) and wiring to controller.
Inspect and test power and ground circuits to the pump and pump controller for proper voltage and continuity. Repair any wiring faults.
Check for blockages or closed valves that reduce pump load. Restore proper flow and retest.
If pump draws unusually low current while overspeeding or shows mechanical noise, consider pump internal failure (impeller slip, worn bearings). Replace pump if required.
If pump and hydraulics are good but commands or feedback are inconsistent, test or reflash the thermal management/EV control module and verify software/calibration. Replace controller if confirmed faulty.
After repairs, clear codes, perform functional test and a road test under the same conditions to confirm the fault does not return.