P2B5A: Engine Coolant Flow Control Valve Control Circuit Low

P2B5A stands for a short to ground in the control wiring of the coolant flow control valve motor. GM's 2025 table for the 3.0-litre Duramax describes the detection: the driver sees more than 9 A flowing, which it interprets as one motor wire touching ground, and 80 out of 100 samples at 12.5 ms set a two-trip Type B fault once relay voltage exceeds 11 V. Unlike P2B58, where the motor itself draws too much current, the cause here is normally insulation damage in the harness, a pinched wire near the valve or water in the connector. The valve stays in its last or default position, so coolant distribution becomes fixed. Short to power is P2B5B, open circuit P2B59.

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

MIL on after two drives
Engine temperature control fixed, slower warm-up or higher running temperature

Most likely causes

Motor wire chafed or pinched against ground
Coolant or water in the valve connector
Internal short to housing in the valve motor

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
With the connector unplugged, check whether the signal wire is making contact with ground.
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 P2B5A means

P: Powertrain: engine and transmission
2: Generic code: same on every make
B: Subsystem depends on the code range
5A: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2B5A?

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 P2B5A?

The most common causes are: motor wire chafed or pinched against ground; coolant or water in the valve connector; internal short to housing in the valve motor.

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.