The Lemon IndexThe engine isn't reaching normal temperature fast enough. Full P0128 page
23 owner complaints · the #1 code GMC Acadia owners name · 23% of GMC Acadia complaints that name a code (every car: 0.8%)
2017–2022 GMC Acadia · most: 2019 (7), 2020 (6), 2018 (4)
GMC Acadia owners named P0128 in 23 complaints to the U.S. government (NHTSA), most often on the 2019, 2020 and 2018 model years. The part they name most is the thermostat (15 complaints). Complaints are owner reports, not proof of a defect.
GMC Acadia model years that report P0128
Owner complaints naming P0128, by model year. Raw counts: years that sold more get more complaints, so this is each model year's record, not a failure rate.
What owners say caused it or fixed it
The most-named part is the thermostat, in 15 of the 23 complaints (65%). 9 of those mention it being replaced or repaired.
- Thermostat15 complaints9 mention a repair or replacement · what GMC Acadia owners paid
5 complaints mention a recall.
Counted from the owners' own words: a part counts when a sentence names it with a cause or repair word. What owners wrote, not a diagnosis. A shop should confirm the cause before replacing parts.
Symptoms owners describe with P0128
30% of these complaints say the check engine light came on.
- Overheats35%8 of 23 complaints
- Warning lights and electrical faults9%2 of 23 complaints
Share of the complaints naming P0128 whose text also describes each problem. A complaint can describe more than one.
Repair costs
GMC Acadia thermostat replacement cost
Keep going
- P0128: meaning, causes and every car that reports it
- GMC Acadia reliability by year
- 2019 GMC Acadia problems and recalls
Other codes GMC Acadia owners report
P0128 on other cars
Chevrolet Blazer (34)
The details
How we count
We read every owner complaint in the NHTSA file whose text names this trouble code, and count the ones filed about this model (matched by the make, model and model year on the complaint). Mileage is what the owner entered on the form.
Parts: a complaint counts for a part when one of the owner's own sentences names that part together with a cause word (failed, bad, diagnosed, caused by, leaking ...) or a repair word (replaced, repaired, new, reprogrammed ...). "Came back" means the same complaint also says the problem returned or the repair didn't fix it. These are counts of what owners wrote, not a diagnosis, and one complaint can name several parts.
Complaints are reports, not proof of a defect, and most owners never file one. Popular models get more complaints, so the counts are not a failure rate. The code meaning is the standard SAE J2012 definition in our own words, or the carmaker's meaning where we verified it for that make.
What P0128 means
The engine isn't reaching normal temperature fast enough. The heater may blow cool and fuel economy drops.
Drive on, get it checked. You can usually keep driving. Have the code read at your next service or within a few weeks.
- Thermostat stuck open
- Faulty coolant temp sensor
- Low coolant
Check the complaints yourself
NHTSA complaint numbers (search them at nhtsa.gov): 11764000, 11753437, 11750068, 11749841, 11749164, 11748973, 11746957, 11741369, 11738997, 11736917, 11735849, 11733007 and 11 more.
Quick answers
What does P0128 mean on a GMC Acadia?
Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature). The engine isn't reaching normal temperature fast enough. The heater may blow cool and fuel economy drops.
Which GMC Acadia years have the most P0128 complaints?
In complaints to NHTSA, owners of the 2019 (7), 2020 (6), 2018 (4) GMC Acadia named P0128 most (23 complaints in all, 2017–2022). Raw counts, not a failure rate.
What fixes P0128 on a GMC Acadia?
Owners most often name the thermostat (15 of 23 complaints). That's what owners wrote, not a diagnosis: have a shop confirm the cause with a scan and tests before replacing parts.
Can I drive my GMC Acadia with P0128?
Drive on, get it checked. You can usually keep driving. Have the code read at your next service or within a few weeks.
Sources: NHTSA owner complaints that name P0128 on the GMC Acadia, counted by The Lemon Index; NHTSA recalls; repair bills owners named. Meanings: SAE J2012 in our own words. Owner reports, not a diagnosis or repair advice for your car.