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DTC codes / P26xx · Computer and output circuits / P261A

P261ACoolant Pump B Control Circuit / Open

P261A indicates that the powertrain control module has detected an open circuit or control fault on the electrical path for Coolant Pump B, which is typically an auxiliary electric pump used for turbocharger or battery cooling. The computer monitors the pump's control circuit and sets this code when the expected voltage or current feedback does not match commanded operation, often due to a wiring break, connector issue, or failed pump.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light, often with no other noticeable symptoms
  • Reduced engine performance or limp mode if the auxiliary pump is critical for cooling
  • Overheating warning or elevated coolant temperature under heavy load or after engine shutdown
  • Auxiliary coolant pump may not run when commanded, leading to heat soak issues
  • Possible smell of coolant or low coolant level if the pump failure caused a leak
  • In some vehicles, a message indicating that the engine is in reduced power mode

Common causes, most likely first

  1. Open or damaged wiring in the coolant pump B control circuit, such as a broken wire or corroded terminal
  2. Failed auxiliary coolant pump B, often due to an open internal winding or seized motor
  3. Poor electrical connection at the pump connector or at the control module, including loose pins or water intrusion
  4. Blown fuse or relay that supplies power to the coolant pump B circuit
  5. Faulty powertrain control module driver for the pump control circuit, though this is less common
  6. Aftermarket accessories or improper previous repairs that disturbed the pump wiring

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules before beginning diagnosis
  2. Inspect the coolant pump B connector and wiring for signs of damage, corrosion, or loose pins, and repair as needed
  3. Check the fuse and relay that supply power to the coolant pump B circuit, replacing any failed components
  4. Measure resistance across the coolant pump B motor terminals to check for an open winding, and compare to specifications
  5. Command the coolant pump B on with a scan tool and listen for operation, while monitoring control circuit voltage and current
  6. If the pump does not operate and wiring is intact, replace the coolant pump B and clear the code
  7. After repairs, clear codes and verify that the pump activates when commanded and that the code does not return

Auxiliary pump failures that mimic wiring faults

  • A seized auxiliary coolant pump can draw excessive current and blow a fuse, which may be misdiagnosed as a simple wiring open circuit until the pump is tested directly.
  • Some vehicles use the auxiliary coolant pump for turbocharger cooling after engine shutdown, so a failure may not cause immediate overheating but can lead to turbo damage over time.
  • The control circuit may be ground-side switched by the powertrain control module, so an open circuit can be on either the power or ground side, and testing only the power wire can miss the fault.
  • Aftermarket coolant pumps or incorrect replacement parts can have different electrical characteristics that trigger P261A even though the pump runs, so always verify part compatibility.
  • A weak or failing battery or charging system can cause voltage drops that set this code intermittently, especially if the pump is commanded during low-voltage conditions.

Can I keep driving with P261A?

It is generally safe to drive short distances at moderate speed to a repair shop, but avoid heavy loads, sustained high-speed driving, or towing because the auxiliary pump may be needed for cooling. If the engine temperature gauge rises above normal or a overheating warning appears, stop safely and shut off the engine.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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