Q: Check Engine code P0128
The Check Engine light is on with the code P0128 for the coolant thermostat (coolant temperature below thermostat regulating temperature).
Recommended Services
| Check Engine Light is on Inspection | $94.99 - $114.99 | Get a Quote |
The cooling system temperature is regulated by thermostat, and the cooling fans order to keep it at optimal temperature for the motor to operate. It does this by keeping the thermostat closed and the fans off until the coolant reaches around 195 to 210 degrees then opens the thermostat to cycle the coolant through the radiator while the cooling fans blow through the radiator cooling the coolant. If the thermostat is stuck open then coolant will never stay inside the motor long enough to heat up to the specified temperature. This would set a P0128. To verify that the thermostat has failed a proper inspection of the Check Engine Light should be called out by a qualified technician, like the one from YourMechanic.
The statements expressed above are only for informational purposes and should be independently verified. Please see our
terms of service
for more details
Get an instant quote for your car
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing
What others are asking
What is the Belt-Minder® system?
Your car has a lot of advanced features. One of those is the Belt-Minder® system. Basically, it’s designed to track seat belt use in your car and alert you to potential problems, keeping you and your passengers safer. The Belt-Minder®...
Shift cable broken
Unfortunately, the most common problem to that symptom is the automatic transmission needs replacing according to our database. I would recommend taking the car to a transmission specialist and have them look at the vehicle.
when i turn my steering wheel to the right--even slightly--my engine stops. why
Hi there, thanks for writing in. I have never experienced this exact issue before. First we should address the vacuum leak, which could cause the car to stall while idling, as well as being a potential cause of the oxygen...
My car cranks but will cut off shorts after starting up. If i start it up again, it will crank but runs and tries to cut off. 2009 Mercedes Benz C300
Hello. Many different faults will cause your 2009 Mercedes C300 to cut off after starting. The most common would be a fuel pump (https://www.yourmechanic.com/services/fuel-pump-replacement), fuel filter (https://www.yourmechanic.com/services/fuel-filter-replacement), battery (https://www.yourmechanic.com/services/battery-replacement), alternator (https://www.yourmechanic.com/services/alternator-replacement), battery cable (https://www.yourmechanic.com/services/battery-cable-replacement), crank sensor (https://www.yourmechanic.com/services/crankshaft-position-sensor-replacement), or camshaft position...
dirty windshield & grill after a road trip
Although bird droppings and smashed highway bugs (https://www.yourmechanic.com/article/how-to-remove-bugs-from-your-car-by-jason-unrau) might not seam like a big deal, it can do end up doing serious damage to the paint of the car costing hundreds of dollars in repairs. Because bugs and bird droppings...
What's wrong with my gas pedal?
Hello. This may be related to what is called a throttle position sensor. This is a small sensor inside the intake system of your car that monitors the position of your foot on the gas pedal and relays this information...
Check Engine Light is on - P0302 and P0304. Ignition coil recently replaced.
The two Diagnostic Trouble Codes, P0304 (https://www.yourmechanic.com/article/p0303-obd-ii-trouble-code-cylinder-3-misfire-detected-by-spencer-clayton) and P0302 (https://www.yourmechanic.com/article/p0302-obd-ii-trouble-code-cylinder-2-misfire-detected-by-jamahl-walker), refer to cylinder misfiring. A faulty ignition coil, spark plug, wire, and so forth can cause a cylinder to misfire but there are other possible causes, too. Consequently, the only...
Buzzing noise from engine compartment
Hello there. Typically a buzzing sound is due to a poor electrical ground; however, does not commonly improve as the vehicle gets warm. Sometimes, a loose serpentine or drive belt, or damaged pulley's that drive these belts can create a...
Oil and battery light keeps coming on
It sounds like you may have a weak battery, a failing voltage regulator or failing alternator. As you may know, the alternator charges the battery while the engine runs by generating amperage and recharging the battery while the engine turns...
Related articles
Symptoms of a Bad or Failing Engine Control Module (ECM)
Common signs of a failing PCM/ECM/ECU include the Check Engine Light coming on, engine performance issues, and the car not starting.
P2261 OBD-II Trouble Code: Turbo/Super Charger Bypass Valve - Mechanical
P2261 P2261 code definition Turbo/Super Charger Bypass Valve - Mechanical What the P2261 code means The P2261 diagnostic trouble code is an indication that the turbo/super charger bypass valve mechanical control circuit is giving the Powertrain Control Module (PCM) a...
P0475 OBD-II Trouble Code: Exhaust Pressure Control Valve Malfunction
What What the P0475 code means The P0475 means that there is something wrong with your exhaust back pressure valve. What causes the P0475 code? There may be more than one cause for the P0475 code. One is a faulty...
Browse other content
Cities
Maintenance
Estimates