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DTC codes / P26xx · Computer and output circuits / P261B

P261BCoolant Pump B Control Circuit Performance/Stuck Off

P261B means the engine control module (ECM) has commanded the electric coolant pump to run, but the pump's control circuit is not responding as expected, so the ECM detects a stuck-off or performance fault. The ECM typically monitors the pump's feedback signal or current draw and sets this code when the circuit stays inactive despite a run command.

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
  • Engine may enter reduced power or limp mode on some vehicles
  • Coolant temperature gauge may climb higher than normal or fluctuate
  • Heater output may be weak or inconsistent because coolant is not circulating
  • Possible overheating warning message or coolant temperature warning light
  • Cooling fan may run constantly or at high speed as the ECM tries to compensate

Common causes, most likely first

  1. Failed electric coolant pump (seized, worn brushes, or internal electronics fault)
  2. Open or shorted wiring in the pump control circuit, including damaged connectors or chafed harness
  3. Blown fuse or faulty relay supplying power to the coolant pump
  4. Poor ground connection at the pump or chassis ground point
  5. ECM software fault or internal driver failure in the pump control circuit
  6. Corroded or loose electrical connector at the pump or ECM
  7. Aftermarket or incorrect pump installed that does not match the vehicle's control strategy

How to diagnose and fix it

  1. Scan all modules for stored codes and freeze-frame data, then verify the coolant pump command and feedback signals with a scan tool
  2. Inspect the pump fuse, relay, and wiring harness for obvious damage, corrosion, or loose connections
  3. Measure voltage and ground at the pump connector while commanding the pump on with the scan tool
  4. Perform a resistance and current draw test on the pump motor to check for an open winding or excessive current
  5. Check for technical service bulletins (TSBs) or software updates for the ECM that address pump control logic
  6. If the circuit tests good but the pump does not run, replace the electric coolant pump and clear codes
  7. After repair, clear codes and run a complete drive cycle to confirm the pump operates and the code does not return

What a stuck-off coolant pump really means

  • A P261B can be set by a pump that runs but does not report the correct feedback signal, so the pump may still circulate coolant even though the code is stored.
  • Some vehicles use the coolant pump for both engine cooling and charge air cooling, so a failed pump can cause performance issues without obvious overheating.
  • A weak or failing battery or charging system can cause the ECM to disable non-essential loads, including the coolant pump, and set this code.
  • Technicians often overlook a poor ground connection at the pump, which can mimic a failed pump and lead to unnecessary replacement.
  • After replacing the pump, some vehicles require a relearn or adaptation procedure with a scan tool to avoid a repeat code.

Can I keep driving with P261B?

It is not safe to continue driving for long distances with this code because the engine may overheat if the coolant pump is truly not running. Limit driving to short trips to a repair shop, and pull over immediately if the temperature gauge rises or a overheating warning appears.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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