DIY Fix - Fault Code P0128 (Coolant Temperature Below Thermostat Regulating Temperature)

In today’s video, Zach takes a deep dive into engine fault code P0128, a diagnostic puzzle that can leave car owners scratching their heads. He covers valuable insights into its causes, symptoms, and how to diagnose and resolve fault code P0128. Is it the thermostat, coolant temperature sensor, cooling fan, or coolant? Whether you're a DIY enthusiast or someone looking to better communicate with your mechanic, this video is for you!
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00:15 - Fault Code P0128 Meaning - Coolant Temperature Below Thermostat Regulating Temperature
00:34 - Most Common Causes for Engine Code P0128
01:00 - The MOST COMMON Cause for Fault Code P0128 - Thermostat
03:15 -Common Cause #2 for Engine Fault Code P0128 - Coolant Temperature Sensor (CTS)
04:34 - Common Cause #3 for Engine Fault Code P0128 - Cooling Fan
06:06 - Common Cause #4 for Engine Fault Code P0128 - Engine Coolant
06:41 - How to Diagnose Engine Fault Code P0128

[@ahoye1]

Thx 4 the in depth explanation of code P0128, this code just came on my Honda Insight and wanted to know what it meant and I went to many google searches and none really explained all of the causes like yours (I mean numerous, many etc...) you're the man, Gracious ;-)

[@8020Media]

A - Thanks for the feedback! Glad you found it helpful.

[@zhanandryan2277]

Love it the way he is explaining very clearly very well and not complicated to be hard to understand thanks very very much

[@8020Media]

Z - Thanks for the feedback. We hope it helped!

[@RhetoricWolf]

Very well spoken and clearly explained. Thank you for this.

[@8020Media]

R - Thanks for the feedback! We hope it helped.

[@Tony-v9z]

Great explanation of p0128 code. Thanks

[@8020Media]

U - Thanks for the feedback! We hope it helped.

[@aaroncarpenter759]

Great explanation, thank you!

[@8020Media]

A - Thanks for the feedback! We hope it was helpful.

[@THEHELLHOUND456]

Thanks for explaining the diagnosis likelihood involving sevondary symptoms and other codes to narrow the most likely cause

[@8020Media]

T - Thanks for the feedback. We hope it was helpful!

[@manolotech1110]

Excellent and complete breakdown.

[@8020Media]

M - Thanks for the feedback! We hope it was helpful.

[@blazeandcyrus]

Really appreciate the tips on coolant temp sensor diags.

[@8020Media]

B - We hope it's helpful!

[@michaelelliott2946]

Excellent information and presented very well!

[@8020Media]

M - Thanks for the feedback! We hope it was helpful.

[@robmyers1956]

THANK YOU FOR A GOOD QUALITY VIDEO YOUR PRESENTATION WAS EXCELLENT

[@8020Media]

R - Thanks for this feedback! We hope it was helpful.

[@MikeBaessler]

Great video and expalation. Thank You.

[@8020Media]

M - Thanks for the feedback! We hope it helps.

[@TheLionInTheArea]

hey man, im getting p0128. if it is the fan running alot even in cold temperatures what can be the cause, is there something like a fan sensor on the fan or something else that may need to be checked or changed. thankyou

[@8020Media]

Probably the coolant temp sensor - if the sensor is bad and sending wrong readings the fan might think it needs to stay on.

[@michaelkryzanski]

Great video. Thanks!

[@8020Media]

M - Thanks for the feedback. We hope it helps!

[@albertg8917]

Informative video. Thanks

[@8020Media]

A - Thanks for the feedback. We hope it helps!

[@tynitty6082]

What if your heat works tho? I changed my sensor my thermostate and wire harnesss and I still get the code my temp drops to C and fan turns on my A/C don’t work but my heat still if I clear the code the A/C will start back working and it a come off of C but engine still doesn’t warm up

[@firstlast-pt5pp]

disconnect the negative battery terminal for 5 minutes and reconnect

[@DamonTheJedi]

Thanks, great video

[@8020Media]

Thanks for the feedback!

[@RobertHinson-p1h]

Very informative

[@8020Media]

R - Thanks for the feedback! We hope it helps.

[@eiyekeye]

Thanks!

[@8020Media]

T - Thanks for the feedback and support!

[@kevinmetcalf6371]

GREAT video... tks

[@8020Media]

Kevin - Thanks for the feedback! We hope it helps.

[@Ckimble]

Does the code need reset or will it go off over time (after replacing thermostat)?

[@8020Media]

C - It would be best to reset, but it will go off after being driven for 50-100 miles if the issue had been addressed.

[@invisibletrailglow836]

Logical, thanks

[@8020Media]

I - Thanks for the feedback!

[@tdoteastend2540]

Got my thermostat replaced almost 2 months ago. This was after noticing my temp gauge stayed at the coldest position all the way left (2017 gmc terrain) and later the C.E.L came on with code P0128. A few times since, with a couple week space in-between each time, I noticed the temp gauge would stop working or stay at the coldest position for a brief period (less than a day) then start working again. Just yesterday the gauge stopped working again. And today the C.E.L came on. I scanned it and code P0128 came back. Also the fan stays on for a minute or 2 after the vehicle has been turned off (same thing happened the first time when thermostat was replaced) Could this be a faulty thermostat that I bought to replace the old one? Or maybe a sensor?

[@8020Media]

T - It certainly could be a sensor related issue. Sounds like it is intermittently failing.

[@tdoteastend2540]

Someone just told me could possibly be a small leak in the thermostat housing. Could this be a possibility as well?

[@8020Media]

T - Could also be a possibility. However, the temp gauge fluctuating points to sensor.

[@MichaelNassios]

Where should I order a new thermostat?

[@8020Media]

M - Need some more information.. What vehicle do you have?

[@MichaelNassios]

@@8020Media 2018 Nissan Murano

[@Motorsports_3]

Can p0135 and p0030 be caused by p0128?

[@8020Media]

M - It's possible.

[@maritesmhayayson8743]

Can we still use the car with this code?

[@8020Media]

M - You can, but we wouldn't advise driving on it for very long. Make sure to stay on top of your coolant levels if you are needing to drive on it.

[@wandacaddell5013]

Do this cause check engine light?

[@8020Media]

Yes, any sort of active fault code will cause a check engine light

[@thaiebony]

I have a 2019 GMC acadia with this code. Repairs at the dealership to change thermostat is $2300. 😢

[@8020Media]

T - Sorry to hear! Thanks for sharing your experience.

[@matthewebel2960]

Yep! I have a 2020 blazer that did the same. I said no way and changed it myself along with the temp sensor. Pain in the butt but worth saving that much.

[@8020Media]

M - Thanks for sharing your experience!

[@jaydee5156]

Okay, let's assume that I've changed the thermostat. The engine is cold. There's new coolant in the system and it's also cold. How will the PCM know? What's going to turn off the check engine light?

[@8020Media]

You can delete the stored code(s) which will get rid of the check engine light. The other option is driving the vehicle until the engine is up to operating temperature. Once the ECU detects the problem is no longer present, it should automatically get rid of the code and CEL.

[@jaydee5156]

@@8020Media Thank you. My daughter is dealing with this on her car. I'm the only one she trusts to fix it for her.

[@8020Media]

J - Keep us updated!

[@eiyekeye]

Thanks!

[@8020Media]

Eiyekeye - Thanks for the support! We hope it helped.