Open circuit in the pump control wire, such as a broken wire or disconnected connector; Short to voltage on the control circuit, often from chafed wiring near hot or moving components; Failed motor electronics coolant pump B (internal open or short); Corroded or damaged electrical connector at the pump or PCM; Faulty powertrain control module (PCM) driver circuit; Blown fuse or relay supplying power to the pump (though this usually sets a low voltage code)

DTC codes / P0Bxx · Hybrid propulsion / P0B3A

P0B3AMotor Electronics Coolant Pump B Control Circuit High

Q: What does code P0B3A mean?

Motor Electronics Coolant Pump B Control Circuit High. P0B3A indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the control circuit for the motor electronics coolant pump B. This pump is typically an electric auxiliary pump used to circulate coolant through the motor electronics, turbocharger, or battery pack, and the high voltage suggests an open circuit, a short to voltage, or a failed pump driver inside the module.

P0B3A indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the control circuit for the motor electronics coolant pump B. This pump is typically an electric auxiliary pump used to circulate coolant through the motor electronics, turbocharger, or battery pack, and the high voltage suggests an open circuit, a short to voltage, or a failed pump driver inside the module.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine performance or limp mode if the pump is critical for cooling
Overheating warning or elevated temperature readings on the dashboard
Cooling fan running excessively or continuously
In rare cases, a no-start condition if the pump is part of the engine control strategy

Common causes, most likely first

Open circuit in the pump control wire, such as a broken wire or disconnected connector
Short to voltage on the control circuit, often from chafed wiring near hot or moving components
Failed motor electronics coolant pump B (internal open or short)
Corroded or damaged electrical connector at the pump or PCM
Faulty powertrain control module (PCM) driver circuit
Blown fuse or relay supplying power to the pump (though this usually sets a low voltage code)

How to diagnose and fix it

Verify the code with a scan tool and check for any related codes in other modules
Inspect the pump connector and wiring for damage, corrosion, or loose pins
Measure resistance of the pump control circuit to check for an open or short
Test the pump motor directly with a known good power source to confirm operation
Check for voltage on the control wire with the key on to identify a short to voltage
If the circuit is intact, test the PCM driver output with a lab scope or substitute a known good PCM
Replace the faulty pump, repair wiring, or reprogram/replace the PCM as needed

Before you replace the coolant pump

A high voltage code on a control circuit often means the circuit is open, not that the pump has failed, so always check wiring continuity before condemning the pump.
Some vehicles use the auxiliary coolant pump for turbocharger cooling after shutdown, and a failure may not trigger noticeable symptoms until the turbo overheats.
The PCM may set this code if the pump control circuit is shorted to battery voltage by a damaged harness rubbing against a hot exhaust component.
A weak or failing battery can cause erratic voltage readings that mimic a high voltage fault, so load-test the battery before deep circuit diagnosis.
After repairs, clear the code and perform a drive cycle that includes both cold starts and full warm-up to confirm the pump operates correctly under all conditions.

Can I keep driving with P0B3A?

It is generally safe to drive short distances to a repair shop, but avoid heavy loads, towing, or sustained high-speed driving because the auxiliary pump may be needed to prevent overheating of critical components. If the engine temperature gauge rises above normal or a warning light appears, stop and shut off the engine immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.