Key takeaways
P0128 means the engine computer timed the warm-up after a cold start and the coolant never got close enough to the thermostat's regulating temperature, most often because the thermostat is stuck open. With a steady light, full coolant and a gauge that never runs hot, you can usually keep driving while you book a diagnosis, but pull over if the gauge climbs toward red.
- 01Check the coolant level with the engine cold, then compare live coolant temperature data, because a faulty sensor, a fan that never shuts off or engine software can set the same code.
- 02Toyota, GM, Mazda, Hyundai, Kia, Subaru and Ford have released P0128 software fixes, and GM and Mercedes-Benz extended thermostat coverage to 15 years or 150,000 miles on some models.
- 03CarMD's 2025 average for a thermostat replacement is $323.59, while RepairPal's national estimate runs $616 to $716, and a bulletin reflash typically lists 0.3 to 0.8 hours of labor.
- 04A cold-running engine runs rich, burns more fuel and keeps its catalytic converter below peak efficiency, so don't leave the code for months.
This guide belongs to our OBD2 guide: most common codes section, which covers the wider topic.
P0128 means your engine took too long to warm up. The engine computer tracks how fast the coolant heats after a cold start, and when it falls short of the thermostat's regulating range in the time allowed, it stores the code. AutoZone's P0128 guide calls it a generic code that can affect most makes and models, and says by far the most common issue behind it is a faulty thermostat.
Most cars drive normally with this code, and a lukewarm heater is often the first sign. The usual fix is a new thermostat, but the code can also come from low coolant, a sensor that reads wrong, a fan that never shuts off or software.
Our table of the most common OBD2 codes and repair costs ties P0128 to thermostat replacement, the only cooling repair on that list, at a $324 national average. This guide adds how carmakers run the test, the live-data checks that prove the cause, and the bulletins that fix some cars with software.
P0128 Quick Answer: Meaning, Severity and Cost
P0128 stands for "Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)." Edmunds' P0128 explainer says it means the engine is not reaching normal operating temperature within a set time frame. With a steady light and a full cooling system, it is usually safe to drive while you arrange a diagnosis.
| Question | Short answer |
|---|---|
| What it means | The coolant did not warm up enough in the time the engine computer allows |
| Most likely cause | A thermostat stuck open or opening too early |
| Other causes | Low coolant, coolant or intake air temperature sensor, fan stuck on, software |
| Severity | Urgent (RepairPal) to not among the more serious problems (CarAdvise) |
| Safe to drive? | Yes with a steady light, full coolant and a gauge that never runs hot |
| Typical cost | $323.59 average for a thermostat (CarMD), $616 to $716 (RepairPal) |
Causes from AutoZone, Kelley Blue Book, Samarins and carmaker bulletins. Severity from RepairPal and CarAdvise. Costs from the 2026 CarMD Vehicle Health Index (2025 repairs) and RepairPal national estimates updated September 3, 2026.
How the engine computer decides the warm-up was too slow
The computer predicts how fast the coolant should warm and checks that against the coolant temperature sensor. Mercedes-Benz's P012800 service document puts it plainly: after engine start, the coolant warms up more slowly than the curve stored in the engine control unit.
Mitsubishi's P0128 test in a 2019 service manual runs only if the coolant is between 14°F and 135°F at start-up and the intake air is 14°F or warmer. It sets the code if the coolant is still below 171°F after the estimated temperature has passed 171°F and the specified time has run out.
RepairPal's P0128 page gives a typical target of 160 to 170 degrees within 15 minutes of start-up, or a rise of at least 70 degrees in extremely cold weather.
California's older OBD II rule, section 1968.1 of its regulations, phased this monitor in from the 2000 model year and required it on all models by 2002. It calls a thermostat faulty if, within a manufacturer-specified time after start-up, the coolant doesn't reach a warmed-up temperature within 20°F of the thermostat regulating temperature, and it lets carmakers skip the test at ambient engine starting temperatures below 20°F. Its successor, section 1968.2, covers 2004 and newer models.
What Temperature Should the Thermostat Open At?
It depends on the engine. Each thermostat has a rated opening temperature, so two engines from the same brand can use different targets.
| Mitsubishi engine (manual year) | Starts to open | Fully open |
|---|---|---|
| 2.0L turbo (2009) | 170°F, plus or minus 3°F | 194°F |
| 2.0L non-turbo and 2.4L (2009) | 180°F, plus or minus 3°F | 203°F |
| 2.4L (2019) | 189°F, plus or minus 3°F | 203°F |
| 3.0L (2019) | 180°F, plus or minus 3°F | 203°F |
From the thermostat inspection pages in Mitsubishi's 2009 and 2019 service manuals. Your engine's rating is in its own service manual.
Mitsubishi tests a thermostat by heating it in stirred water and noting when the valve opens, as its 2009 thermostat inspection page describes.
Samarins' P0128 guide says the coolant reading should be close to the outside temperature on a cold engine and about 180 to 220°F after roughly 10 minutes of driving. Kelley Blue Book uses 200°F for a correctly working system.
P0128 Symptoms
Often the only sign is the check engine light. TechShop Magazine's Code Reader column says there may be no driveability problem at all, and the temperature gauge may read normal or low.
- A heater that blows lukewarm air or takes a long time to warm up
- A gauge that sits low, or coolant temperature that drops on the highway in cold weather
- Lower fuel economy
- Cooling fans that keep running, sometimes after the engine is off
- A failed emissions inspection
Symptoms from Kelley Blue Book, Edmunds, AutoZone, Samarins, 1A Auto and GM's special coverage N242484760.
Kelley Blue Book's P0128 page stresses that P0128 measures how fast the coolant warms and does not mean the engine is overheating. That is a separate code, P0217.
What Causes P0128? Most Likely First
The thermostat is the usual culprit, but the coolant level and sensor reading take minutes to check, so start there.
A thermostat stuck open or opening too early
AutoZone points to a thermostat that is leaking or stuck open. The 2026 CarMD Vehicle Health Index ranks thermostat replacement ninth among 2025 check engine repairs, at 2.44 percent, and blames a thermostat stuck open, rust, a lack of coolant changes or exposure to extreme temperatures.
A thermostat can also leak past its seal. Samarins lists a seal that lets coolant bypass a closed thermostat, and Acura's NSX bulletin 17-048 says the inner seal can detach and hold the thermostat open.
Some open too soon. Subaru's bulletin 09-56-13 says coolant can enter the thermostat's internal piston during a long cold soak, so it opens below its specified temperature. GM's 2021 Camaro coverage, below, describes the same early opening.
Low coolant or air in the system
Low coolant is the easiest fix, and AutoZone makes it the first check. CarAdvise adds air trapped in the coolant passages, which it says to bleed out.
If the level keeps dropping with no visible leak, our guide to white smoke from the exhaust explains the tests for an engine that is burning coolant.
A coolant or intake air temperature sensor that reads wrong
A sensor can report a cold engine when it isn't. FCA's STAR case S2118000009 has technicians check the coolant temperature sensor before the thermostat: resistance between its metal shell and connector pin 1 should be greater than 1 megohm, or the sensor is replaced.
Kelley Blue Book says most vehicles have two coolant temperature sensors, one for the engine computer and one for the gauge. Samarins also lists a faulty intake air temperature (IAT) sensor, and CarAdvise adds damaged or corroded sensor wiring or connectors.
A cooling fan that won't shut off
A fan that runs all the time keeps the engine cold. Carista's P0128 explainer says a fan stuck on keeps the coolant below the regulating temperature and points to the fan relay or sensor if it stays on after the engine cools.
1A Auto's fan and P0128 guide adds that the computer may run the fans on high to prevent overheating when the sensor, engine or thermostat has a problem, so a running fan can be a result as well as a cause.
Engine computer software
Some P0128 codes come from the software. GM says the code on some 2019 to 2020 Silverado 1500 pickups can come from the diagnostic running at the incorrect time, and Kia's bulletin ENG206 says some 2016 to 2017 Optima 1.6T models light up with P0128 even though there are no system faults.
Cold weather, idling and long downhill runs
Kelley Blue Book says winter driving in a cold climate can leave the engine unable to reach normal temperature. Subaru's Forester bulletin 09-75-21 says the code may set while the engine is below operating temperature on continuous downhill roads, and fixes it with new engine computer logic.
Idling is a slow way to warm up. The fueleconomy.gov cold weather page says engines warm faster when driven, and that most manufacturers recommend driving off gently after about 30 seconds.
Electronic thermostats and coolant control valves
Many newer engines control coolant flow electronically. Subaru's June 2022 TechTIPS says models with a thermo control valve (TCV), such as the 2019 and newer Forester, should not get a traditional thermostat, and that an overfilled CVT can push the valve into Rapid Cooling mode and set P0128.
Heated thermostats have their own circuit code. Kelley Blue Book's P0597 page names it Thermostat Heater Control Circuit/Open, and Mercedes-Benz tests the heating element before replacing the thermostat.
How to Diagnose P0128 With a Scanner
Prove the cause with live coolant temperature data before buying parts. A scanner with live data and freeze frame does the job, as our roundup of the best OBD2 scanners explains.
- Read every code and save the freeze frame. Mazda uses freeze frame temperatures to decide whether its fix applies, and Toyota's applies only if P0128 is the only code.
- Check the coolant level and strength with the engine cold, against your service manual.
- Look up bulletins and software updates by VIN.
- Compare coolant and intake air readings after an overnight soak. Samarins says the coolant should read close to the outside temperature, and 1A Auto flags large gaps between the two.
- Graph coolant temperature on a cold-start drive. Samarins expects about 180 to 220°F after about 10 minutes.
- Feel the radiator hose as the engine warms. Kelley Blue Book says one that warms slowly suggests a thermostat stuck open, and one that heats too fast means checking the sensor.
- Watch the fans. Carista says to confirm they aren't running continuously.
- Repair, clear the code and repeat a cold-start drive.
Reading the warm-up curve
| What the live data shows | What it suggests |
|---|---|
| Cold-engine reading far from outside temperature | Coolant or intake air temperature sensor fault |
| Slow climb that levels off below normal | Thermostat stuck open or opening early |
| Normal warm-up, then a drop at highway speed | Thermostat stuck open, worse in cold weather |
| Reading that jumps, spikes or drops out | Sensor, connector or wiring fault |
| Normal curve, but the code keeps setting | A software bulletin may apply |
Patterns from Samarins, 1A Auto, Kelley Blue Book, AutoZone, CarAdvise and the GM and Toyota bulletins. Each needs a test to confirm.
Don't replace parts a bulletin says to keep
GM's Silverado bulletin tells technicians not to replace the thermostat or any other components for this condition unless diagnostics point to a fault, and Mazda's fix needs no new PCM, only a calibration update.
Carmaker Bulletins That Mention P0128
Check for one before you buy parts. Most fix the code with an engine computer update, and two extend thermostat coverage.
| Maker and bulletin | Vehicles | Fix described |
|---|---|---|
| GM 20-NA-167 | 2019 to 2020 Chevrolet Silverado 1500 with the LV3 engine, plus GMC Sierra 1500 | Reprogram the ECM, no parts needed |
| GM N242484760 | 2021 Chevrolet Camaro | New thermostat, covered 15 years or 150,000 miles |
| Toyota T-SB-0045-13 | 2010 to 2011 Camry, 2AR-FE with automatic | ECM reflash |
| Mazda 01-021/13 | 2013 CX-5, certain 2010 to 2013 Mazda3, early 2012 Mazda5 | PCM calibration update |
| Hyundai 19-01-016H-1 | Certain 2018 Elantra GT and 2019 Veloster, 1.6L Turbo | ECM software update |
| Subaru 09-56-13 | Certain 2011 to 2014 Forester, Impreza, XV Crosstrek, Legacy, Outback and BRZ | Countermeasure thermostat |
| Subaru 09-75-21 | 2019 to 2021 Forester | ECM reprogram |
| Ford 25-2348 | 2022 F-53 and F-59, 2023 F-650/F-750 and E-Series, 7.3L | PCM update |
| Mercedes-Benz extended warranty | 2019 to 2023 models with M176, M177 and M178 engines | Software update, then thermostat if needed |
From each maker's bulletin as filed with NHTSA. Each applies only to the listed vehicles and VINs, so ask a dealer to confirm yours.
GM's Silverado bulletin 20-NA-167 reprograms the ECM with a calibration that updates the coolant temperature diagnostic, with no parts required.
Toyota's Camry bulletin T-SB-0045-13 modifies the control logic to reduce the chance of the code setting and covers the reflash under Toyota's Federal Emission Warranty of 96 months or 80,000 miles.
Mazda's bulletin 01-021/13 blames improper PCM control logic and lists 0.3 hours of labor. On 2010 Mazda3s, the fix applies only when the freeze frame shows coolant between 172°F and 176°F, which is why saving the freeze frame matters.
Hyundai's bulletin 19-01-016H-1 revises the P0128 logic and states that there are no drivability symptoms associated with the code.
Ford's bulletin 25-2348 covers an incorrectly lit light with P0128, P0420 or P0430 on 7.3L trucks and vans and blames PCM software, allowing 0.7 to 0.8 hours.
Because the same Ford update covers two catalyst codes, our P0430 catalyst system efficiency code guide explains what those mean and how the converter test works.
Extended thermostat coverage from GM and Mercedes-Benz
GM's special coverage N242484760 says some 2021 Camaro thermostats may open at a lower temperature than intended, causing P0128, coolant leaks near the housing or fans that run after shutdown. Dealers replace it at no charge for 15 years or 150,000 miles from the original in-service date.
Mercedes-Benz's January 2025 update says a thermostat sealing ring on some 2019 to 2023 models could detach and delay coolant warm-up. It extends coverage from 4 years or 50,000 miles to 15 years or 150,000 miles.
Is It Safe to Drive With a P0128 Code?
Usually, yes, if the light is steady, the coolant is full and the gauge never climbs toward hot. The bigger risk is a cooling problem hiding behind the code.
Sources split on urgency. RepairPal rates P0128 Urgent, meaning immediate action is necessary. Edmunds says short trips are generally safe but not to ignore it for long, and CarAdvise's P0128 page suggests service within a couple of weeks.
| What you notice | Severity | What to do |
|---|---|---|
| Steady light, full coolant, gauge normal or low | Low to moderate | Drive normally and diagnose within a couple of weeks |
| Coolant low or dropping | High | Top up with the engine cold and find the leak before long trips |
| Fans running constantly or after shutdown | Moderate | Check the fan relay, wiring and coolant sensor |
| Gauge climbing toward hot or a red temperature warning | Severe | Pull over when safe and switch the engine off |
Summarizes RepairPal, Edmunds, CarAdvise, AutoZone and 1A Auto. A hot gauge means overheating, a different problem from P0128.
Never open a hot cooling system
AutoZone warns that opening a hot coolant system could cause burns and other injuries. Let the engine cool completely before you remove the reservoir or radiator cap.
Free tool
Check Engine Light Checker. Say whether the light is steady, flashing or came on and went off, tick a red temperature warning or rough running if you have them, and get a Low risk, Act soon or Stop and check ruling.
The Check Engine Light Checker treats a red temperature warning as a reason to stop and check, whatever code is stored.
What P0128 Does to Fuel Economy, Heat and Emissions
An engine that stays cold costs fuel and runs dirtier. TechShop Magazine says a cold engine runs rich, emissions are high, and the catalytic converter doesn't reach maximum efficiency until the engine is fully warm.
Fueleconomy.gov says city gas mileage is roughly 15 percent lower at 20°F than at 77°F, partly because the engine takes longer to reach its most fuel-efficient temperature. Edmunds adds that oil stays thicker in a cold engine, increasing wear, and Kelley Blue Book lists a heater that doesn't work as it should.
How to Fix P0128 and What It Costs
Fix what the tests prove: top up and bleed the coolant, apply a bulletin's software update, or replace the thermostat or sensor.
| Repair | RepairPal estimate | Other published figure |
|---|---|---|
| Check engine light diagnosis | $125 to $183 | Not listed |
| Thermostat replacement | $616 to $716 | CarMD: $323.59 |
| Engine coolant temperature sensor | $499 to $585 | Not listed |
| Engine computer update under a bulletin | Not listed | 0.3 to 0.8 hours of labor in the bulletins above |
RepairPal national estimates for parts and labor, updated September 3, 2026, before taxes and fees. CarMD average for 2025 U.S. repairs from its 2026 Vehicle Health Index; the same report's thermostat profile lists $314. Labor times from the Mazda, Toyota and Ford bulletins.
RepairPal's thermostat estimate splits the job into $421 to $429 for parts and $195 to $286 for labor. The technician drains the coolant, removes the housing, cleans the sealing surface, fits a new gasket, then refills and bleeds the system. RepairPal also warns that leak stopper products can eventually clog the radiator and heater core.
RepairPal's coolant temperature sensor estimate puts parts at $343 to $356 and labor at $156 to $229, and calls the swap typically easy for a moderately experienced DIYer once the sensor is confirmed faulty.
Shop time explains most of the gap. AAA's 2026 labor rate guide says most mechanics charge $120 to $159 an hour, and dealers often charge 25 percent or more above independent shops.
Free tool
Repair Cost Estimator. Enter the parts price, labor hours, shop rate and fees from your quote, pick Thermostat to compare with its $324 national average, and see the total and the parts-only DIY cost.
Run a thermostat quote through the Repair Cost Estimator to see how much of the bill is labor before you approve the work.
Does a warranty cover P0128 repairs?
Sometimes. The EPA's emissions warranty FAQ gives 8 years or 80,000 miles only to the catalytic converters, the emissions computer and the OBD device, and 2 years or 24,000 miles to other emission-related parts, used cars included.
Toyota and Mazda both list their P0128 software fixes under their federal emissions warranties. A thermostat sits outside the 8-year list unless a carmaker extends it, as GM and Mercedes-Benz have.
Avoiding a repeat after a new thermostat
Installation mistakes bring the code straight back. A 2013 bulletin on file with NHTSA for the 2010 to 2013 Kia Forte, numbered PS267, traces repeat P0128 codes after a thermostat replacement to a thermostat installed out of position. Its fix is to line the thermostat up with the tab on its housing, and it says no movement should be possible once it is installed correctly.
After the Repair: Clearing P0128
Clear the code, let the car cool completely and repeat a cold-start drive. EPA's 1995 OBD rule lets the light go out on its own if the malfunction doesn't recur during three subsequent sequential trips in which the monitor runs.
Mercedes-Benz has technicians let the car cool for at least 8 hours after clearing the code, then test drive until the coolant reaches at least 158°F (70°C). Mitsubishi's P0128 confirmation drive needs at least 14°F outside and cruising at 32 mph or more until the coolant reaches 153°F, so a short idle won't prove the repair.
Codes Related to P0128
Companion codes often explain why the warm-up test failed.
| Code | Meaning | What it tells you |
|---|---|---|
| P0125 | Insufficient Coolant Temperature for Closed Loop Fuel Control | Another slow warm-up check |
| P0126 | Insufficient Coolant Temperature for Stable Operation | A related warm-up check |
| P0117 | Engine Coolant Temperature (ECT) Sensor Circuit Low Input | A sensor circuit fault |
| P0118 | Engine Coolant Temperature Sensor Circuit High | A sensor circuit fault |
| P0113 | Intake Air Temperature Sensor 1 Circuit High Input | An IAT fault that can skew the check |
| P0597 | Thermostat Heater Control Circuit/Open | An electronic thermostat fault |
| P0217 | Engine Coolant Over Temperature Condition | Overheating, the opposite problem |
Code names from CarAdvise, Edmunds and Kelley Blue Book. AutoZone says P0125 is related to P0128 on most vehicles.
Treat P0128 as a cooling system question: check the coolant cold, watch the warm-up curve, look for a bulletin, then replace the thermostat. For coolant types and service intervals, see the cooling system and AC section of our car maintenance guide.
Frequently Asked Questions
What does P0128 mean on a Chevy Silverado?
It means the same slow warm-up, but GM has a known software cause on some trucks. Its bulletin 20-NA-167 for the 2019 and 2020 Silverado 1500 with the LV3 engine, which also lists the GMC Sierra 1500, says the P0128 diagnostic can run at the incorrect time. The fix is an ECM reprogram, and GM tells technicians not to replace the thermostat unless diagnostics find a real fault.
What does P0128 mean on a Honda or Acura?
Honda's service bulletin for the 2017 Acura NSX labels P0128 Cooling System Malfunction, but the meaning matches the generic code: the coolant did not warm up as expected. That bulletin names a thermostat inner seal that detaches and holds the thermostat open as the possible cause, and the fix is a new thermostat. On a Civic or any other Honda, check for a bulletin by VIN first.
Can I replace my car thermostat myself?
On many cars, yes, if you can drain, refill and bleed the cooling system. RepairPal describes the job as draining coolant, removing the housing, cleaning the sealing surface and fitting a new gasket. Labor varies widely: Subaru lists 1.0 to 1.1 hours, GM 2.5 hours on the 2021 Camaro, and Acura 4.1 hours on the NSX. A Kia Forte bulletin warns that a misplaced thermostat brings P0128 back.
Where is the coolant temperature sensor located?
It varies by engine, so check your service manual. TechShop Magazine says the sensor sits before the thermostat, and Kelley Blue Book says most vehicles have two coolant temperature sensors, one feeding the engine computer and one for the gauge or warning light. 1A Auto notes the sensor is easier to replace than the thermostat and often doesn't require draining coolant.
Can I drive with a bad coolant temperature sensor?
For a short time, if the engine runs well, but don't put it off. RepairPal says a faulty coolant temperature sensor can cause rough running, poor acceleration, decreased fuel economy and even overheating. FCA's technical case shows how to test one, and RepairPal recommends a proper diagnosis before replacing any parts, because the same symptoms can point to a different fault.
Can a P0128 code go away on its own?
Sometimes. EPA's OBD rule lets the check engine light switch itself off after three trips in a row in which the monitor runs without finding the fault. That doesn't prove the cause is gone. O'Reilly notes that clearing a code only turns the light off temporarily, and that the light will likely come back if the problem is bigger than a code or sensor reset.
Sources and References
- AutoZone. P0128: Coolant Thermostat Temperature Below Regulating Temperature
- Edmunds. P0128: Coolant Temperature Below Thermostat Regulating Temperature
- Kelley Blue Book. P0128 Code: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)
- Kelley Blue Book. P0597 Code: Thermostat Heater Control Circuit/Open
- RepairPal. P0128 OBD-II: Coolant Temperature Below Thermostat Regulating Temperature
- RepairPal. Thermostat Replacement Cost Estimate
- RepairPal. Engine Coolant Temperature Sensor Replacement Cost Estimate
- RepairPal. Check Engine Light Diagnosis & Testing Cost Estimate
- CarMD. 2026 CarMD Vehicle Health Index
- AAA. Average Mechanic Labor Rate: Repair Costs in Your State 2026
- CarAdvise. Diagnostic Trouble Code P0128
- TechShop Magazine. The Code Reader: P0128
- Samarins. Code P0128: Coolant Temperature Below Thermostat Regulating Temperature
- Carista. P0128 Code Explained: Causes and Fixes
- 1A Auto. P0128 Code Appeared or Radiator Cooling Fan Won't Turn Off?
- O'Reilly Auto Parts. Check Engine Light DTC Code P0128: Coolant Temperature Below Thermostat Regulating Temperature
- Kelley Blue Book. P0217 Code: Engine Coolant Over Temperature Condition
- Edmunds. P0113: Intake Air Temperature Sensor 1 Circuit High Input
- Edmunds. P0117: Engine Coolant Temperature (ECT) Sensor Circuit Low Input
- Mitsubishi Motors. DTC P0128: Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature), 2019 Service Manual
- Mitsubishi Motors. DTC P0128 Description and Confirmation Procedure
- Mitsubishi Motors. Thermostat Inspection, 2009 Service Manual
- Mitsubishi Motors. Thermostat Inspection, 2019 Service Manual
- Cornell Law School LII (California Code of Regulations). Cal. Code Regs. Tit. 13, § 1968.1: Malfunction and Diagnostic System Requirements, 1994 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines
- Cornell Law School LII (California Code of Regulations). Cal. Code Regs. Tit. 13, § 1968.2: Malfunction and Diagnostic System Requirements, 2004 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles and Engines
- U.S. DOE and EPA (fueleconomy.gov). Fuel Economy in Cold Weather
- U.S. EPA. Frequent Questions related to Transportation, Air Pollution, and Climate Change
- U.S. EPA (Federal Register). Regulations Requiring On-Board Diagnostic Systems: Revision to Requirements for Storage of Engine Conditions Associated With Extinguishing a Malfunction Indicator Light (August 2, 1995)
- General Motors (via NHTSA). Bulletin 20-NA-167: Malfunction Indicator Lamp (MIL) Illuminated, DTC P0128 Set
- General Motors (via NHTSA). Special Coverage N242484760: Engine Coolant Thermostat
- Toyota Motor Sales USA (via NHTSA). T-SB-0045-13: MIL ON DTC P0128
- Mazda North American Operations (via NHTSA). Service Bulletin 01-021/13: Multi Model, MIL On With DTC P0128:00
- Hyundai Motor America (via NHTSA). TSB 19-01-016H-1: DTC P0128 ECM Software Update
- Kia (via NHTSA). TSB ENG206: 1.6T GDI ULEV MIL ON Logic Improvement for P0128
- NHTSA (filed bulletin; issuer not named on the document). Bulletin PS267: Thermostat Re-Installation Procedure, Repeat Repair (DTC P0128), 2010-2013 Forte
- Subaru of America (via NHTSA). Bulletin 09-56-13: Countermeasure Thermostat Availability for DTC P0128
- Subaru of America (via NHTSA). Bulletin 09-75-21: DTC P0128 / Coolant Thermostat
- Subaru of America (via NHTSA). TechTIPS, June 2022: Diagnosing P0128 on Thermo Control Valve Equipped Vehicles
- Ford Motor Company (via NHTSA). TSB 25-2348: Incorrectly Illuminated MIL With DTC P0128, P0420, And/Or P0430
- American Honda, Acura (via NHTSA). Service Bulletin 17-048: MIL Comes On With DTC P0128
- FCA US (via NHTSA). STAR Case S2118000009: MIL On, DTC P0128 Set in the PCM
- Mercedes-Benz AG (via NHTSA). LI20.10-P-060902: Engine Diagnosis Warning Lamp Activated, Fault Code P012800
- Mercedes-Benz USA (via NHTSA). Emission Extended Warranty: Engine Thermostat (incl. Software Update) MY19-23
Written by
CarTipsMentor Team
Researched from the sources listed above and checked against them before publishing. Nobody paid to be mentioned on this page. It is general information, not advice about your own vehicle.
Published . Last updated .
