P261F: Coolant Pump A Control Circuit Stuck On

P261F means electric coolant pump A reports activity while the module has it switched off. GM's 2025 ECM table 25OBDG04B describes the test: with the pump commanded off or below 299 rpm for 2 s and more than 11 V on board, a feedback speed of 3,100 rpm or more for 8 of 10 seconds sets the code as Type B; the warning lamp follows on the second faulty trip. Bulletin 22-NA-077 shows how that can fail without a defect: on 2021-2022 Blazer, Acadia, XT5 and XT6 with the 3.6 L LGX, high engine speed pushes so much coolant through the auxiliary pump that its impeller free-spins above the limit; GM reflashes the ECM and warns against replacing the pump. Mercedes lists P261F71 on the OM651 Sprinter with vacuum leaks or a damaged water pump. P261E is pump B.

Medium severity. Can I keep driving?Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

Symptoms

Check engine lamp after two faulty trips
Usually no noticeable driveability change
Slower warm-up when the pump really keeps running

Most likely causes

Impeller driven by main pump flow at high rpm, fixed by ECM software (GM)
Vacuum leak or contaminated switching valve of a switchable pump (Mercedes OM651)
Pump electronics reporting wrong speed or not switching off

What to check, in order

Start with the simplest. You can tick off each step.

With the engine cold, check the coolant level; never do this when the system is hot
Use the scanner to command the movement and compare the actual position with the requested one.
Check the actual temperature in live data
Make sure the fan comes on when it should
Check the thermostat and connector
Measure the sensor and replace it if its readings do not make sense

Good to know

Repair difficulty: medium
It affects emissions.

What each character of P261F means

P: Powertrain: engine and transmission
2: Generic code: same on every make
6: Control modules and outputs
1F: Specific fault in that system

Frequently asked questions

Can I keep driving with code P261F?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P261F?

The most common causes are: impeller driven by main pump flow at high rpm, fixed by ECM software (GM); vacuum leak or contaminated switching valve of a switchable pump (Mercedes OM651); pump electronics reporting wrong speed or not switching off.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.