P0128 on a 2022 Chevrolet Silverado 1500 Ltd

P0128 means the engine warmed up slower than expected or stayed cooler than the computer expected.

Not your vehicle? See general P0128 info.

Most common causes on the 2022 Chevrolet Silverado 1500 Ltd

Ranked from 577 NHTSA owner complaints filed for this vehicle.

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1
Electronic coolant control valve failure (functions as the L87's thermostat)
Medium severity
An owner had the coolant control valve fail outright, causing a coolant leak, fans running continuously, and the engine sporadically failing to reach/hold temperature before derating; this valve is the electronic equivalent of a thermostat on this engine.
Reported in 1 NHTSA complaint
Parts:coolant control valve
2
Cooling-system fault tied to NHTSA engine-cooling campaign 25V274000
Medium severity
A separate owner's truck displayed an 'Engine Oil Hot' cooling warning and had an open NHTSA Engine and Engine Cooling campaign, indicating cooling-system regulation problems on this platform that can also manifest as slow warm-up.
Reported in 1 NHTSA complaint
3
Stuck-open thermostat
Medium severity
A conventional wax-pellet thermostat failing to close fully is the classic cause of this code on most engines, keeping coolant flowing to the radiator continuously.
Common cause
Parts:thermostat
4
Failed/out-of-range engine coolant temperature (ECT) sensor
Low severity
A drifting ECT sensor reports a temperature that never reaches the commanded regulating point even when the engine is actually up to temperature.
Common cause
Parts:coolant temperature sensor
5
Low coolant level
Low severity
Insufficient coolant slows warm-up and can prevent the engine from reaching operating temperature inside the monitor's time window.
Common cause
6
Cooling fan stuck running continuously
Low severity
A fan that won't shut off due to a relay or control-module fault keeps pulling heat out of the coolant, preventing the engine from reaching setpoint.
Common cause
Parts:cooling fan relay

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0128 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Weak cabin heat
Poor fuel economy
Temperature gauge low
Long warm-up time

What to check before replacing parts

Check coolant level when the engine is cold

Look for: Low coolant reduces the system's ability to reach and hold operating temperature — top off and recheck before assuming the thermostat or sensor is at fault.

Compare scan-tool coolant temperature to actual warm-up time

Look for: An engine that takes noticeably longer than normal to reach operating temperature (or never gets there) on the scan tool, with normal coolant level, points to the thermostat rather than the sensor.

Inspect thermostat operation

Look for: A thermostat stuck open (or opening at the wrong temperature) lets coolant circulate through the radiator too early, keeping the engine running cooler than it should — this is the most common cause of this code.

Check cooling fan command

Look for: A fan that runs constantly or turns on too early (commanded on when temperature is still low) keeps the engine from warming up normally, mimicking a stuck-open thermostat.

Inspect coolant temperature sensor data

Look for: A sensor reading that doesn't rise smoothly with actual engine warm-up, or that reads implausibly low compared to how the engine feels/behaves, points to a sensor or wiring fault rather than a true cooling problem.

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