2007 GMC P0128: What It Means & Is It Safe to Drive?
P0128 on the 2007 GMC: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature). Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
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What this code means
The engine is not reaching normal operating temperature in the expected time. Usually a stuck-open thermostat.
Common causes on the 2007 GMC
- Thermostat stuck open
- Coolant temperature sensor fault
- Low coolant level
Symptoms
- Check Engine Light
- Heater may blow cold
- Poor fuel economy
- Temperature gauge stays low
Typical fixes
- Replace thermostat
- Replace coolant temperature sensor if faulty
- Refill coolant and check for leaks
Repair cost range
For a 2007 GMC, repairs for P0128 typically fall between $100 and $350, depending on the root cause and labor rates in your area.
Known issues on GMC
GMC P0128 shares all the same thermostat concerns as Chevrolet given the identical drivetrains. The plastic stat housing on the 3.6L LFX and 5.3L V8 should be inspected for cracks during replacement.
Most commonly affected models
Sierra 2007–2013Terrain 2010–2015Acadia 2007–2012