P261C: Coolant Pump B Control Circuit Low

What it means

Voltage on the second coolant pump control line is below the expected window. Usually a short to ground or a shorted motor winding.

At a glance

• Usually lights the check-engine light

How it works

Coolant Pump B is an electric pump for a separate cooling loop, and its control circuit carries the electrical signal used to operate it. P261C sets when the control-line voltage falls below the expected range, often because the wire is shorted to ground or the pump winding is shorted.

Common causes

Most likely first.

1. Control wire shorted to ground
2. Motor winding short
3. Connector pins corroded - high contact resistance

Symptoms

• Check-engine light
• Possible overheating or reduced cooling in the loop served by the pump

How to diagnose it

1. Check freeze-frame data and live temperatures to determine whether the Pump B loop was demanding cooling when the low-voltage fault occurred.
2. With the system safely cool, inspect Pump B's control wiring and connector for chafing to ground, corrosion, moisture, or damaged terminals.
3. Use the wiring diagram to test the control line for a short to ground and compare circuit readings with the manufacturer's specification.
4. Check the Pump B motor winding for a short using the manufacturer's procedure and specification.
5. If the wiring and winding pass, test the controller's Pump B output according to the vehicle's service information.

Common fixes

• Clean and secure corroded or loose Pump B connector terminals.
• Repair control wiring that is shorted to ground or damaged.
• Replace Pump B if its winding is confirmed shorted.
• Repair the controller output only after the pump and wiring test correctly.

Can I keep driving?

Avoid driving if the Pump B loop is overheating or its temperature warning appears; otherwise, limit use and monitor temperatures. A shorted control circuit can disable circulation and may also stress the pump circuit.