P2B29: Hybrid/EV Battery Pack Coolant Pump A Overspeed

A centrifugal pump that suddenly spins faster while drawing less current has lost its liquid: it is churning air. P2B29 reports exactly this for battery coolant pump A. Porsche describes the detection for the 2018 Panamera 4 E-Hybrid, where the pump watches its speed and current draw against the commanded speed and reports a dry run to the battery controller, but files it as P0C4A00 and notes it may take hundreds of miles to appear. Ford uses P2B29 itself: bulletins 20-2221 (2020 Escape HEV built up to 10 June 2020, stored in the BECM), 20-2293 and 20-2345 (hybrid Explorer, Aviator and Police Interceptor Utility) list it among MIL codes cured by reprogramming. Outside such software cases, look for leaks, low level or poor bleeding. P2B28 is the general performance code.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

MIL or hybrid system warning
Pump audibly gurgling or whining
Battery power or charging limited

Most likely causes

Air in the battery coolant loop after service or incomplete bleeding
Leak in a battery cooling line lowering the level
Battery controller software misjudging pump feedback (Ford 2020 hybrids)

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

Repair difficulty: medium
It can trigger limp mode.
It affects emissions.

What each character of P2B29 means

P: Powertrain: engine and transmission
2: Generic code: same on every make
B: Subsystem depends on the code range
29: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2B29?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P2B29?

The most common causes are: air in the battery coolant loop after service or incomplete bleeding; leak in a battery cooling line lowering the level; battery controller software misjudging pump feedback (Ford 2020 hybrids).

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.

P2B29: Hybrid/EV Battery Pack Coolant Pump A Overspeed - Dry Run