P2B29: Hybrid/EV Battery Pack Coolant Pump A Overspeed - Dry Run
The hybrid control module detects that battery pack coolant pump A is running above the calibrated maximum speed without load. Indicates dry running due to coolant loss or air ingestion.
What P2B29 means
P2B29 is a generic OBD-II powertrain code in the hybrid & EV group.
- Check engine light
- Usually on
- Emissions-related
- No
- Limp mode possible
- Yes
- Drive cycle to clear
- Not required
Get it fixed
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Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
Common causes
- 01Coolant loss in battery loopMost likely
- 02Air drawn into pump suctionPossible
- 03Pack cell imbalance approaching service thresholdLess likely
Can I drive with P2B29?
Have it checked before relying on the car.
High-voltage faults can shut the drive system down without much warning. Do not open orange high-voltage components; this needs a trained technician.
Why we rate it urgent
- High-voltage system fault: the car may shut down or refuse to start
- Can put the vehicle in limp mode (reduced power)
- Turns on the check engine light
Severity is our rule-based rating from the code’s flags in OBDex and the system it affects, not an inspection of your car. If the check engine light is flashing, or you notice overheating, low oil pressure, or brake or steering problems, stop driving and get help.
How to diagnose P2B29
- 1
Confirm the code and save freeze-frame data
Read the codes with an OBD-II scan tool and note every code, not just P2B29. Save the freeze-frame data (speed, load, temperature when the fault set) before clearing anything; it tells you when the fault happens.
- 2
Fix other faults first
If other codes are stored, start with power-supply, sensor-circuit and communication codes. They can cause this code as a side effect.
- 3
Check live data
Watch the related sensor and actuator readings in live data (Hybrid battery coolant pump A, Battery pack coolant loop) and compare them with expected values in the service information for your vehicle.
- 4
Test the likely causes in order
Start with the most likely cause and work down: Coolant loss in battery loop; air drawn into pump suction; pack cell imbalance approaching service threshold. Test before replacing parts.
- 5
Check for recalls and service bulletins
Look up recalls for your exact vehicle with its VIN, and ask a dealer about technical service bulletins (TSBs). Manufacturers sometimes issue software updates or extended warranties for known faults.
- 6
Clear the code and verify the repair
After the repair, clear the code and drive the car under the conditions in the freeze-frame data to confirm it does not return.
P2B29 repair cost estimate
Estimate, not a quote. Labor times are typical ranges for this code from OBDex, and $125/hr is an assumed rate. Shop rates and labor times vary by vehicle and region. Diagnosis time may be billed separately.
- DIY difficulty
- Hard
- Good DIY job?
- Usually a shop job
Involved testing or major parts. Most owners use a shop.
Parts and systems involved
- Hybrid battery coolant pump A
- Battery pack coolant loop
P2B29 FAQ
What does P2B29 mean?
P2B29 means “Hybrid/EV Battery Pack Coolant Pump A Overspeed - Dry Run”. The hybrid control module detects that battery pack coolant pump A is running above the calibrated maximum speed without load. Indicates dry running due to coolant loss or air ingestion.
Is P2B29 serious? Can I keep driving?
We rate P2B29 as urgent severity. Have it checked before relying on the car. High-voltage faults can shut the drive system down without much warning. Do not open orange high-voltage components; this needs a trained technician.
What causes P2B29?
The most common causes, from most to least likely: Coolant loss in battery loop; Air drawn into pump suction; Pack cell imbalance approaching service threshold. Test before replacing parts, because several causes can set the same code.
How much does it cost to fix P2B29?
Typical labor is about $125–$750 at an assumed $125/hour shop rate, plus parts. That is an estimate, not a quote: labor times and rates vary by vehicle and region, and diagnosis may be billed separately.
Can I fix P2B29 myself?
DIY difficulty is hard. Most owners leave this to a shop because it needs involved testing or specialist tools. Always confirm the cause before buying parts.
Will P2B29 clear itself?
If the fault was intermittent, the warning may go off once the computer stops seeing it, but the code stays in memory. Fix the cause; clearing the code alone doesn’t repair anything.