P261B: How to Diagnose & Fix — Coolant Pump "B" Control Circuit Range/Performance
5 vehicles · 5 makes · $250-$2,200 repair
How to diagnose and fix P261B: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
BMW 3 Series · 2012–2013
BMW SIB 01 13 21 identifies 2012-2013 E92/E93 335i, 335is and 335i xDrive Coupe vehicles with N54T or N55 engines in the electric coolant-pump settlement population. The bulletin provides a diagnosis-and-repair path when a warning or fault is present; it does not call for preventive replacement on every N55 3 Series.
Common Symptoms
- Engine warning lamp
- Engine-overheat warning
- Reduced-power operation may accompany overheating
How to Fix
Stop safely if an overheat warning appears and avoid continued operation until the cooling system is checked. Verify the chassis, engine and VIN, read fault memory and follow the current coolant-pump test plan before replacement. Settlement benefits were time-limited.
Sources for this issue (1)
Toyota Prius · 2010–2015
Unlike a belt-driven pump, the 2ZR-FXE engine coolant pump is a brushless electric unit commanded by duty cycle from the ECM. The internal motor/controller degrades and the pump slows or stops, so coolant stops circulating through the engine. The ECM detects the speed feedback falling below threshold and sets P261B (or P261C), lights the check engine and hybrid warning lights, and will shut the gas engine down to protect it, leaving the car crawling on battery only. Toyota addressed it with T-SB-0143-10 and a revised pump design; it is one of the most-reported repairs on third-gen Prius, Prius v, Prius c and Lexus CT200h.
Common Symptoms
- Check engine light with hybrid system warning
- Engine temperature climbing, overheat message
- No coolant movement visible in the reservoir with engine running
- Gas engine shuts down or car enters limp mode
- Heater blows cold
How to Fix
Confirm with the code plus a visual check of coolant flow in the reservoir with the engine running. Replace the electric engine water pump with the updated Aisin/Toyota unit (do not reuse the old O-ring), refill and run the Techstream/manual air-bleed procedure - trapped air in this system will cause repeat overheat codes and can mimic a second pump failure. It is a 1-2 hour job accessible from the passenger side of the engine. Cheap no-name aftermarket pumps are a common repeat-failure complaint.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Aisin WPT-190 electric engine water pump
replace an engine coolant pump proven slow, electrically faulty or non-operational after circuit diagnosis Fitment/availability: 2010-2015 Prius 1.8L 2ZR-FXE; Aisin also catalogs the branch for 2012-2015 Prius Plug-in and 2012-2018 Prius…
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Sources for this issue (3)
Audi A6 · 2005–2023
Water pump failures are common across all A6 generations due to plastic impeller degradation and seal leaks. Audi uses plastic impellers that crack or disintegrate over time (typically 80,000-120,000 miles), causing coolant leaks and overheating. The water pump is often driven by the timing belt or timing chain, so replacement is recommended during timing service to save labor. Thermostat housings also crack due to heat cycling, causing coolant leaks and erratic temperature readings. Symptoms include coolant leaks under the car, overheating in traffic, temperature gauge fluctuations, and coolant warning lights. Ignoring a failed water pump can lead to severe engine overheating, warped cylinder heads, and blown head gaskets ($3,000-$5,000 repair). Some models have electric auxiliary water pumps that also fail, causing poor heater performance.
Common Symptoms
- Coolant leak under front of car (pink/green puddle)
- Overheating in stop-and-go traffic or at idle
- Temperature gauge rising above normal (middle position)
- Coolant warning light or low coolant message
- No heat from cabin heater (auxiliary pump failure)
- Hissing or gurgling noise from engine bay
- Steam or coolant smell from engine
How to Fix
Replace water pump AND thermostat together ($800-$1,500 with labor). Always use OEM or high-quality aftermarket parts (Rein, Hepu) and avoid cheap pumps. If water pump is timing belt/chain driven, replace during timing service to save labor. Flush cooling system and refill with the Audi coolant specified for the vehicle (G12++ and G13 are fully compatible; mixing other types reduces corrosion protection, so check Audi's mixing chart). Inspect coolant hoses and replace if cracked. If auxiliary electric water pump fails, replace separately ($300-$600). Monitor coolant level weekly and address leaks immediately to prevent overheating damage.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Beck/Arnley 131-2517 main engine water pumpCross-refBeck/Arnley 131-2517
Confirm VIN and current fitment before ordering; this is not an auxiliary water pump.
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipPhotograph the suspected leak before cleaning it, then recheck after the system is filled and the car is driven. The Audi bulletin requires the leak to be reproduced rather than inferred from old residue.
- WarningConfirm that the failed component is the main engine coolant pump. The A6 also has auxiliary pumps, and those are different parts with different repair roles.
Sources for this issue (2)
Cadillac CT5 · 2020–2021
Mercedes-Benz GLE · 2020–2025
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P261B code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P261B mean?
P261B stands for "Coolant Pump "B" Control Circuit Range/Performance." This code sets when the engine control module commands the electric (auxiliary) coolant pump "B" but the circuit's behavior or feedback does not match what is expected for the commanded state. Coolant pump "B" is typically an electric auxiliary pump that helps circulate coolant for engine, turbo, hybrid, or A/C-related cooling. A range/performance fault means the pump or its control circuit is responding sluggishly or incorrectly, which risks overheating if coolant is not moving properly.
What are the most common causes of P261B?
The most common causes of P261B are: Failing or seized electric auxiliary coolant pump, Wiring or connector fault in the pump control circuit, Corroded or loose pump connector, Low coolant level or air in the system, Faulty pump relay or power supply, Control module (ECM) driver fault (less common). The specific cause varies by vehicle.
How much does it cost to fix P261B?
Repair costs for P261B range from $250 to $2,200, depending on the vehicle and root cause.
Which vehicles are affected by P261B?
Au7o has documented P261B across 5 vehicle models from 5 manufacturers: Audi, BMW, Cadillac, Mercedes-Benz, Toyota.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.