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P261BCriticalPowertrain

P261B: How to Diagnose & Fix — Coolant Pump "B" Control Circuit Range/Performance

5 vehicles · 5 makes · $250-$2,200 repair

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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.

Toyota Prius · 2010–2015

Link to this issueError Codes:P261BP261C

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…

    PartsGeek

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Typical repair cost:$250 - $800
Sources for this issue (3)
  • 2010 Prius with P261B water pump failure - PriusChatforum
  • P261B Code Water pump failure - PriusChatforum
  • Engine Code P261B Water Pump - PriusChatforum

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Community Reported
High ConfidenceVerifiedReviewed Aug 2026

BMW 3 Series · 2012–2013

Link to this issueError Codes:P0217P261B

BMW SIB 01 13 21 identifies 2012-2013 E92/E93 335i, 335is and specified xDrive coupe/convertible 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 support preventive replacement for every 2012-2018 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. ShowMeTheParts resolved five 2012 335i water-pump candidates, but fitment does not prove failure or remedy, so no commerce link is approved.

Sources for this issue (1)
  • BMW SIB 01 13 21 - E92/E93 Electric Coolant-Pump Settlement and Diagnostic Scopetsb

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NHTSA Verified
High ConfidenceVerifiedReviewed Jul 2026

Mercedes-Benz GLE · 2020–2025

Link to this issueError Codes:P261B

The 3.0L M256 inline-six (GLE 450, AMG GLE 53 on the W167) is prone to oil leaks from the oil filter housing/adapter assembly, which integrates the engine oil cooler with coolant passages, making leaks both oil and coolant related. The M256 also relies on an electric coolant pump and an auxiliary electric water pump that can fail, producing erratic cooling behavior and overheating warnings. Because oil and coolant circuits share the adapter, an internal cooler leak can let coolant migrate into the oil and quickly damage the engine. Owners also report cold-start timing-chain rattle and oil consumption past ~60k miles on this engine.

Common Symptoms

  • oil spots under engine
  • coolant loss
  • low coolant / overheating warning
  • erratic temperature gauge
  • oil and coolant mixing
  • cold-start timing chain rattle
  • oil consumption between services

How to Fix

Pressure-test the cooling system and inspect the oil filter housing/adapter and integrated oil cooler for seepage; replace the housing gaskets/seals or the complete adapter as needed and refresh coolant. Test the electric coolant pump(s) and replace failing units. Investigate any coolant-in-oil immediately to prevent bearing damage. Monitor oil level between services given the engine's oil-consumption tendency.

What you need to fix it

Only diagnosis- and fitment-reviewed repair parts are linked here.

  • Genuine Mercedes-Benz M256 oil-filter housing A2561801500
    OEMMercedes-Benz A2561801500

    Confirmed failed M256 oil-filter housing on the cataloged GLE450/GLE53 branch Fitment/availability: The inspected direct U.S. Confirm VIN, installed part/supersession

    FCP Euro
  • Genuine Mercedes-Benz M256 main engine water pump A2562002200
    OEMMercedes-Benz A2562002200

    Confirmed failed main coolant-pump branch on the specifically cataloged M256 GLE450/GLE53 application Fitment/availability: The inspected direct U.S. Confirm VIN, pump

    FCP Euro

As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.

Typical repair cost:$600 - $2,200
Sources for this issue (2)
  • Mercedes M256 Engine: Full Guide and Known Issues - Mercedes Assistancearticle
  • 2018-2023 Mercedes M256 Engine Oil Filter Adapter Leaks - Go-Partsarticle

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026

Cadillac CT5 · 2020–2020

Link to this issueError Codes:P0217P261B

GM issued a TSB (December 2020) stating the printed circuit board inside the electric water pump on affected CT4/CT5 vehicles may have been manufactured incorrectly, potentially causing a water pump failure; when this occurs the vehicle displays warnings as coolant temperatures rise, the oil pressure gauge falsely indicates high oil pressure, a reduced power/torque message appears, and if ignored the AC is disabled and the driver is told to turn off the engine . The 2.0L LSY turbo-four (base engine in the CT5) is one of the engines susceptible to this water pump failure (the other being the 2.7L L3B, which is not used in the CT5) .

Common Symptoms

  • High coolant temperature warning
  • Oil pressure gauge falsely reading high
  • 'Reduced engine power' message
  • AC compressor cut out
  • 'Turn off engine' chime/message
  • No coolant flow at idle

How to Fix

Dealers inspect and, if necessary, replace the entire water pump assembly; the job takes roughly four hours and was performed at no cost to the owner under the Customer Satisfaction Program TSB . The TSB coverage window ran through December 31, 2022, so out-of-warranty owners now face out-of-pocket cost . Independent shop cost for the electric pump assembly typically runs $700–$1,400 parts plus labor. Diagnose by scanning for coolant temp DTCs and observing the false-high oil pressure indication, which is a hallmark of this specific failure mode.

Typical repair cost:$0 - $1,400
Sources for this issue (1)
  • GM Customer Satisfaction Program N202320510 - Water Pump Failuretsb

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Community Reported
High ConfidenceLast reported by owners May 2026Reviewed May 2026

Audi A6 · 2005–2023

Link to this issueError Codes:P261AP261BP261CP261DP0128

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)—cheap pumps fail within 20,000 miles. If water pump is timing belt/chain driven, replace during timing service to save labor. Flush cooling system and refill with OEM Audi G12++ or G13 coolant (do NOT mix types). 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 pump
    Cross-refBeck/Arnley 131-2517

    Confirm VIN and current fitment before ordering; this is not an auxiliary water pump.

    eBay

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.
Typical repair cost:$800 - $1,500
Sources for this issue (1)
  • Audi TSB 2071515/1 - 2020-2024 A6 2.0 TFSI coolant-pump leak diagnosistsb

Research This Issue

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Community Reported
Medium Confidence

Find P261B by make

Browse every documented model and issue for your make.

Audi · 1 issueBMW · 1 issueCadillac · 1 issueMercedes-Benz · 1 issueToyota · 1 issue

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.

Related codes

  • P2614 · Camshaft Position Signal Output Circuit/Open
  • P261A · Coolant Pump "B" Control Circuit/Open
  • P261C · Coolant Pump "B" Control Circuit Low
  • P261D · Coolant Pump "B" Control Circuit High
  • P0020 · Camshaft Position 'A' Actuator Circuit (Bank 2)
  • P0034 · Turbocharger/Supercharger Bypass Valve Control Circuit Low
  • P0035 · Turbocharger/Supercharger Bypass Valve Control Circuit High
  • P003A · Turbocharger/Supercharger Boost Control 'A' Position Exceeded Learning Limit
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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.

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