My 2014 Dodge Charger threw a check engine light last week while my wife was driving home from work. After a brief read from my scan tool it was revealed that the error code is was P0128. Most likely culprit, the thermostat!
What is a P0128 error code?
The official meaning for the P0128 error code is “Coolant Temperature Below Thermostat Regulating Temperature” In plain English the car is basically saying that after a predetermined amount of time the coolant temperature has not come up to normal operating temperature. In other words the car is to cold! Modern fuel injected engines like to run at their specified operating temperature, and in the short term this is mainly a nuisance check-engine light, in the long run it could damage you engine and should be addressed.
What can cause a P0128 error?
The most common cause is a faulty engine thermostat, however the coolant temperature sensor, intake air temp sensor, faulty engine fans, or even dirty or low coolant can be the issue as well. For the purpose of this blog post I am going to focus on the thermostat, which is the most common issue.
Dodge Charger 3.6L V6 Normal Operation
My Charger has a digital temperature gauge that can be accessed via the engine information screen on the dash board. During normal operation at 40° outside you can see the car warm up to OT (about 208°) and then cycle the thermostat. (198° then back up to 208°). While the thermostat was stuck in the open position the max OT @ 65mph was only 185°, which is lower than the allowable OT and will trip the check engine light.
What parts and tools do i need to repair this?
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You will also need some coolant to replace whatever is lost. Make sure you use coolant that is compatible for your year. My 2014 uses Mopar OAT coolant. About $24/ gallon from Amazon
If your Charger has high mileage you may want to flush your coolant while doing the work.
This is the part your going to replace. Thermostat for the pentastar 3.6l v6.
Other items you should have on hand, screw drivers, socket wrench, torque wrench.
How to replace the thermostat
The most important part of this job to make sure the car is cool. Hot engine coolant is pressurized and will cause severe burns if opened hot. Please allow sufficient time for the engine to cool before working on the coolant system. ** Side note, coolant is poisonous to humans and animals. Please do not leave coolant anywhere it can be ingested by pets or children.
Step one is to remove the intake. There are two hose clamps, one on the air filter box and the other on the throttle plate. Slide the hose off lift the assembly and put to the side. There are electrical connections on the hose take care not to break them
Once the intake is out of the way, use a pair of pliers to slide the hose clamp out of the way. Coolant will begin pouring out of the hose and engine block it would be wise to have a bucket or tray under the car to catch the fluids. Also take care to keep the coolant off the drive belt if possible.
Two 10mm bolts hold the thermostat to the block. Remove and take the thermostat off. Replaced with an equivalent part.
When tightening the bots they should be torqued to 110inch pounds.
re-install the radiator hose, and intake. Fill the coolant reservoir to the appropriate level and run the car. Look for leaks! Also keep an eye on the temperature gauge to watch for overheating (If there is air in the system the car could overheat.)
In the case of air in the system at the top of the thermostat there is a bleed-off-valve. Use a screwdriver to slowly turn the valve until air / coolant leaks out. Tighten when done.
I hope this information was helpful.
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