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DTC codes / P26xx · Computer and output circuits / P261D

P261DCoolant Pump B Control Circuit High

P261D indicates that the engine control module (ECM) has detected an abnormally high voltage on the control circuit for coolant pump B, which is often an auxiliary or secondary electric pump used for charge cooling or cabin heating. The ECM expects a specific voltage range on the circuit and sets this code when the signal exceeds the upper threshold, typically indicating an open circuit, short to power, or a faulty pump.

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

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp).
  • Often no symptoms besides the warning light, especially if the main coolant pump is still functioning.
  • Possible reduced performance or power derating if the auxiliary pump is critical for charge cooling.
  • Inability to maintain proper cabin heat in vehicles that use the pump for heater circuit flow.
  • Overheating warnings or elevated engine temperatures in specific driving conditions if the pump is essential for cooling.
  • A stored code in the ECM with no noticeable change in vehicle behavior.

Common causes, most likely first

  1. Open circuit in the control wire between the ECM and the coolant pump B, such as a broken wire or disconnected connector.
  2. Short to voltage on the control circuit, often due to chafed wiring contacting a power source.
  3. Failed coolant pump B (electric pump) with an internal open or short that affects the control circuit.
  4. Corroded or damaged electrical connector at the pump or ECM, causing high resistance or intermittent connection.
  5. Faulty ECM driver circuit for the pump control, though this is less common.
  6. Aftermarket accessories or improper wiring repairs that interfere with the control circuit.

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related codes in other modules.
  2. Inspect the coolant pump B connector and wiring for damage, corrosion, or loose pins.
  3. Measure resistance of the pump control circuit to check for an open or short to voltage.
  4. Test the coolant pump B directly by applying power and ground to confirm operation.
  5. Check the ECM connector for corrosion or poor terminal tension at the control circuit pin.
  6. Repair any wiring faults found, such as splicing a broken wire or replacing a damaged connector.
  7. Clear the code and perform a road test to verify the repair, monitoring live data if available.

Before you replace the auxiliary coolant pump

  • A high voltage on the control circuit often means the circuit is open, so the ECM sees a pulled-up voltage; this can be caused by a simple unplugged connector rather than a failed pump.
  • Some vehicles use coolant pump B for charge air cooling on turbocharged engines, and a failure may not trigger overheating but can cause reduced power and poor fuel economy.
  • The code can be set by a short to voltage from a nearby circuit that chafes against the pump wiring, so inspect for wire routing issues after accidents or repairs.
  • Do not assume the pump is bad; test the control circuit with a multimeter and a wiring diagram before condemning the pump, as misdiagnosis is common.
  • On certain models, the auxiliary pump runs only under specific conditions (e.g., after engine shutdown), so a lack of immediate symptoms does not mean the system is functioning correctly.

Can I keep driving with P261D?

You can generally continue driving if the only symptom is the warning light and engine temperature remains normal, but avoid heavy loads or sustained high-speed driving if the auxiliary pump supports charge cooling. If overheating warnings appear, stop and seek service immediately.

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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