I need a reliable and quick response to my concern. My check engine light is on and I checked for the code. It shows me the P0128 code related to the coolant system running low temperature. I read somewhere that the risk is low, but should get it checked out within a month. My problem is I’m in Tennessee and will be driving back to Louisiana on Monday, 800 miles. Should I be concerned about the drive or not? I’d like to wait and get it checked out at home, not on vacation. Thanks
Engine Code P0128 2017 JK
- Thread starter rjohn
- Start date
I would think as long as you watched your temp you'd be ok. Have you popped your hood while it's running to see if it smelled or looked hot?
Sure have. No smell or leaking fluids. I pretty much assumed your response, but thanks. When I get home, if it’s still on, I may have the local mechanic I use check it out for me.
A low coolant system warning does not mean your coolant (and engine) will not reach normal operating temperature. It means that it is taking too long. The computer expects your engine to reach normal operating temperature within something like 15 minutes of being started. This matters because the catalytic converter(s) don't work properly at lower temperatures, which means the O2 sensor data is off, which means the computer cannot adjust timing and air/fuel mixtures to their optimal state, which means you will be down a bit on power and mileage and up a bit on emissions. Not good.
Start by checking for leaks. A leak will prevent the system from pressurizing, which results in a lower boiling point for the coolant. Checking is easy. Start the engine. Get it warm. Leave it running. Pop the hood. Look for coolant where there shouldn't be any coolant. Basically, anywhere outside the cooling system.
Next concern would be a stuck thermostat. If it is stuck open, coolant flows through the radiator when it's not hot, and that prevents the engine from reaching normal operating temperature as quickly as it should.
This doesn't sound like any big deal, but bear in mind that most engine wear occurs when the engine is running cold. Cold moving bits have more play in them, which equals more wear. It's not going to wear out an engine in a week, but it absolutely will decrease the overall life of the engine. And stuck open is better than stuck closed.
If you're a long way from home, I'd check for leaks immediately, and if that's not the problem, it's probably safe to drive it home before you dive into it.
Start by checking for leaks. A leak will prevent the system from pressurizing, which results in a lower boiling point for the coolant. Checking is easy. Start the engine. Get it warm. Leave it running. Pop the hood. Look for coolant where there shouldn't be any coolant. Basically, anywhere outside the cooling system.
Next concern would be a stuck thermostat. If it is stuck open, coolant flows through the radiator when it's not hot, and that prevents the engine from reaching normal operating temperature as quickly as it should.
This doesn't sound like any big deal, but bear in mind that most engine wear occurs when the engine is running cold. Cold moving bits have more play in them, which equals more wear. It's not going to wear out an engine in a week, but it absolutely will decrease the overall life of the engine. And stuck open is better than stuck closed.
If you're a long way from home, I'd check for leaks immediately, and if that's not the problem, it's probably safe to drive it home before you dive into it.
Wow, what an explanation. Very thorough and understandable, thank you. I’ll check for leaks tomorrow. I also checked my antifreeze reservoir, cold, and it was at the “full” mark, but there could still be a slow leak, I assume. Great advice by all, thanks. I’ll post the solution as soon as I find out the problem.
I am with @Dirty Dog on this. I would suspect the thermostat might be staying open which is causing it to take longer than usual to reach operating temperature therefore or not running consistently at the right temperature causing the computer to throw the MIL light on. Check the fluid level including the reservoir bottle and for leaks. If all is good you should be fine. Long term is the engine can build up sludge from from being too cool. I think there is also a possibility of slightly less fuel economy.
My P0128 was a stuck open thermostat. I ran it for a few weeks like that till I got the parts delivered. Get Mopar replacement and not some replacement OEM. Worth it in the long run. I went with Mopar antifreeze too. Just DO NOT mix the different antifreezes!
Yep. Had the same code. I posted an extensive, detailed diagnostic and corrective path I took some time back in this forum.
Typically a stuck open thermostat will cause this. Easiest diagnosis:
With a cold engine, have someone start your JK with your hand wrapped around the upper radiator hose and if you can feel flow immediately or within a few seconds of start up, this is the first indicator the t-stat is open. It's not supposed to open until the engine is at operating temp, and when it iopens, that's when you should get coolant flow through the hose.
This first test is the easiest, doesn't cost a penny and will almost always give the info you need to either begin looking elsewhere or just replace the t-stat.
And, as JJ stated above, make sure you get an OEM t-stat. Get the option with the housing, which is black ABS plastic. Much easier to install that putting a new t-stat in the old housing. Partsgeek.com was the cheapest and quickest ship time, that's where I got mine.
Typically a stuck open thermostat will cause this. Easiest diagnosis:
With a cold engine, have someone start your JK with your hand wrapped around the upper radiator hose and if you can feel flow immediately or within a few seconds of start up, this is the first indicator the t-stat is open. It's not supposed to open until the engine is at operating temp, and when it iopens, that's when you should get coolant flow through the hose.
This first test is the easiest, doesn't cost a penny and will almost always give the info you need to either begin looking elsewhere or just replace the t-stat.
And, as JJ stated above, make sure you get an OEM t-stat. Get the option with the housing, which is black ABS plastic. Much easier to install that putting a new t-stat in the old housing. Partsgeek.com was the cheapest and quickest ship time, that's where I got mine.
OEM parts are sourced based on low bid. It's not like Jeep is making (for example) O2 sensors. The idea that the NTK O2 sensor you buy directly from NTK will somehow be lower quality than the exact same sensor bought from Mopar just doesn't make sense.
Yes, I know. Your friends brother Bob's cousin bought an NGK sensor and it didn't work. But there are just as many people who bought them from Mopar and got bad ones. Because they're the same part.
Quality parts are quality parts. OEM just means adding a middleman, for most things.
Never had an issue with O2 sensors. Been running Bosch for years with no problems at all. But I can tell u this. When your 4th wife LuLu calls with a problem, and u send her to Starving Marvin’s auto for a wheel speed sensor, a cam sensor or a crank sensor And u tell her to get anything that fits. U will have to crawl under her again real soon
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I think there is a lot of reason to buy OEM when those parts will be monitored/operated /controlled/calibrated by the ECM. This forum is replete with owners who have experienced nothing but headaches when installing non-OEM parts and codes being thrown left and right because the ECM isn't recognizing them.
With respect to the t-stat issue as described by the OP, the OEM t-stat from partsgeek.com I purchased was absolutely the least expensive option possible. And it had the Mopar name on it, so getting a refund if it was bad was no big deal.
The "gotcha" is that with OEM, you are (theoretically) getting a part spec'd to your vehicle and motor. With OTC or mail order there's always and element of chance. You have your vehicle torn apart, the part arrives, and it is not what you needed. This can happen even with OEM, but with OEM you have a clear target to complain to/shout at. Reputable manufacturers - e.g. Bosch - are or were less of a risk. These days, a lot of even allegedly "high end" parts are not made where you expect them to be made. The real differences come down to proper quality control. If the "name" owners are concerned with maintaing goodwill, they have conscientious QA inspectors working to insure that anything with their imprint meets some proper standards. Decades ago a I wanted a bandsaw. I researched various brands with crazy differences in prices. What I discovered was that the saw frames, and pulley covers, were essentially identical, regardless of brand. And the add-ons fit most brands. The saw frames were all cast in the foundry in China, regardless of brand. You just paid for the assurance that someone had checked the equipment for obvious problems, some trivial perfume on the pig, and the brand. I bought a cheap one, added all the pieces I wanted, and still use it. The same goes for most car parts. It's just more work to take them out and replace them if the QA person was on a tea break when the part went by.