p0128
Easy Fix
Chevrolet · SUVs
Coolant Thermostat Below Regulating Temperature
Quick Answer
Error code P0128 on your Chevrolet SUVs means: Coolant Thermostat Below Regulating Temperature. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
CL14636CL14606Blazer LT 2024Blazer Premier 2024Blazer RS 2024Equinox Activ 2024Equinox LT 2024Equinox RS 2024Suburban High Country 2024Suburban LS 2024Suburban LT 2024Suburban Premier 2024Suburban RST 2024Tahoe High Country 2024Tahoe LS 2024Tahoe LT 2024Tahoe Premier 2024Tahoe RST 2024Tahoe Z71 2024Trailblazer Activ 2024Trailblazer LS 2024Trailblazer LT 2024Trailblazer RS 2024Traverse LS 2024Traverse LT 2024Traverse Premier 2024Traverse RS 2024Traverse Z71 2024Trax Activ 2024Trax LS 2024Trax LT 2024Trax RS 2024CL14526CL14506CK10906CK10706CL14456CL14806CL14416
Likely Causes
How to Fix It
1
Check coolant level in the reservoir and radiator; top off and bleed air if low
2
Use a scan tool to monitor engine coolant temperature during warm-up
3
Verify the cooling fans are not running continuously at cold start
4
Remove the thermostat and test its opening temperature in heated water
5
Replace the thermostat and housing gasket if it opens below rated temperature
Pro Tip
This is a common issue that most users can resolve without specialized tools. Try the first step before moving on to more complex solutions.
Parts You May Need
Thermostat
Thermostat housing gasket
Engine coolant
ECT sensor (if faulty)
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