P2B63: Coolant Pump B Stuck/Stalled

What it means

Coolant pump B reports a stuck/stalled condition. Coolant circulation through the affected loop cannot be commanded reliably.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Coolant pump B moves coolant through its assigned loop, and the control module checks whether the pump responds and turns as expected when commanded. P2B63 sets when the pump is detected as stuck or stalled, so coolant flow through that loop may stop even if the electrical command is present.

Common causes

Most likely first.

1. Pump impeller jammed by debris
2. Motor seized

Symptoms

• Check-engine light
• Engine or a coolant-cooled component may run hotter than usual
• Cabin heat or cooling performance may be reduced

How to diagnose it

1. Review freeze-frame data and live pump B command, speed, or status readings alongside affected-loop temperatures to confirm when the stall was detected.
2. With the vehicle safely powered down, inspect pump B and its coolant connections for leaks, impact damage, or signs of blockage.
3. Check the coolant level and inspect the affected loop for debris or conditions that could obstruct pump B's impeller.
4. Command pump B with a scan tool and compare its response with the manufacturer's procedure, keeping clear of moving parts and hot coolant.
5. If the loop is unobstructed and pump power and ground are correct, test the pump for a seized motor or impeller and replace it if it cannot turn as specified.

Common fixes

• Correct low coolant or repair a leak, then fill and bleed the loop as specified.
• Clear debris obstructing the pump or its coolant passage, where serviceable.
• Repair damaged pump wiring or connector contacts if checks show a supply fault.
• Replace coolant pump B if its motor or impeller is seized.

Can I keep driving?

Avoid driving if the affected loop is overheating, and stop safely if engine or component temperature rises. Pump B stalling can stop coolant circulation, worsen overheating, and may cause the vehicle to limit power.