What causes a P0128 code on GM

How to fix a P0128 code and service engine soon light on GM vehicles

Since a P0128 code is defined as Engine Coolant Temperature (ECT) Below Thermostat Regulating Temperature, many people automatically replace the thermostat. It’s not an expensive part, but it most likely won’t fix the P0128 code and it will pop up again.

GM has issued a service bulletin 09-06-02-004A to address the problem on the vehicles listed below

2009 Buick Enclave

2009 Chevrolet Traverse

2009 GMC Acadia

2009 Saturn OUTLOOK

All vehicles equipped with the 3.6L Engine AND Built Prior to VIN Breakpoints listed below:

Buick 9J191884

GMC Acadia 9J191884

Saturn Outlook 9J191884

Chevrolet Traverse 9S143279

The service bulletin advises you to check the coolant level before proceeding. If the system is full, REPROGRAM the PCM with updated software. This is the fix for the problem. You can get the vehicle reprogrammed at any dealer or independent shop that’s has updating capabilities.

Your vehicle may be covered under the 8 year / 80,000 mile (130,000 km) emission controller warranty, so check with the dealer first

©, 2016 Rick Muscoplat