p0128
Moderate
Cadillac · SUVs
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
Quick Answer
Error code P0128 on your Cadillac SUVs means: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature). This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Check coolant level and top off if needed
2
Monitor coolant temperature with scanner
3
Allow engine to warm up completely
4
Replace thermostat if stuck open
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Thermostat
Coolant
Temperature gauge
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