P2B5E: Engine Coolant Flow Control Valve Position Sensor Circuit Low

P2B5E reports a position sensor reading below its valid window. On GM's 3.0-litre Duramax the valve sends its angle as a raw SENT value in percent of 5 V; anything under 2 % counts as too low, and 80 failures in 100 samples at 6.25 ms set a Type B fault, provided there is no SENT communication fault and the relay supplies more than 11 V. A broken 5 V reference, a sensor ground issue inside the valve or a damaged signal wire can produce such a value. GM includes P2B5E in the LM2 chafed-harness condition of bulletin 21-NA-149. The engine computer loses the actual position and stops closed-loop control of coolant flow. High reading: P2B5F; plausibility: P2B60.

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
Coolant flow no longer regulated, warm-up slower

Most likely causes

5 V reference or signal wire interrupted or shorted to ground
Chafed engine harness on GM LM2 (21-NA-149)
Position sensor in the valve faulty

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 P2B5E means

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

Frequently asked questions

Can I keep driving with code P2B5E?

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 P2B5E?

The most common causes are: 5 V reference or signal wire interrupted or shorted to ground; chafed engine harness on GM LM2 (21-NA-149); position sensor in the valve faulty.

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.