P261D: Coolant Pump B Control Circuit High

What it means

Voltage on the second coolant pump control line is above the expected window. Typical causes are a short to battery or an open motor winding.

At a glance

• Usually lights the check-engine light

How it works

Coolant Pump B is an electric pump that circulates coolant through a separate vehicle-specific loop. P261D sets when the control-line voltage is higher than expected, which can result from a short to battery power or an open Pump B motor winding.

Common causes

Most likely first.

1. Control wire shorted to B+
2. Open motor winding
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. Review freeze-frame data and live temperatures to determine whether Pump B was being commanded when the high-voltage fault set.
2. With the system safely cool, inspect the Pump B connector and control-wire route for corrosion, loose pins, damage, or contact with a power feed.
3. Using the wiring diagram, check the control line for a short to battery voltage and compare the result with the manufacturer's specification.
4. Test Pump B's motor winding and control-wire continuity using the manufacturer's procedure.
5. If the wiring and winding pass, check the controller's Pump B output for a fault.

Common fixes

• Clean and secure corroded or loose Pump B connector pins.
• Repair control wiring shorted to battery power or otherwise damaged.
• Replace Pump B if its motor winding is confirmed open.
• Repair or replace a failed controller output after verifying the pump and wiring.

Can I keep driving?

Avoid driving if the Pump B loop is overheating or a temperature warning appears; otherwise, keep trips short and watch temperatures. Without reliable Pump B control, the loop it serves may lose circulation and overheat.