P2B58: Engine Coolant Flow Control Valve Motor Current High

P2B58 reports that the electric motor driving the engine coolant flow control valve draws too much current. GM documents the check for its 3.0-litre inline-six Duramax diesel: in the 2025 table 25OBDG04B the driver stage flags a current above 5.5 A, and 80 failures in 100 samples taken every 12.5 ms set a Type B fault, so the MIL follows on the second trip. Enabling needs more than 11 V on the powertrain relay and an engine that is not cranking. A seized rotary valve, debris in the housing or a motor with shorted windings are typical reasons. GM bulletin 21-NA-149 lists P2B58 for LM2 trucks with a chafed engine harness. Heating and warm-up may suffer while the valve is stuck.

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 the second drive with the fault
Slow warm-up or weak cabin heat
Fans may run more often as a precaution

Most likely causes

Rotary valve stiff or seized from deposits or debris in the housing
Valve motor with shorted turns
Chafed engine harness on GM LM2 (bulletin 21-NA-149)

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
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
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: hard
It affects emissions.

What each character of P2B58 means

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

Frequently asked questions

Can I keep driving with code P2B58?

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 P2B58?

The most common causes are: rotary valve stiff or seized from deposits or debris in the housing; valve motor with shorted turns; chafed engine harness on GM LM2 (bulletin 21-NA-149).

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.