2012 chevrolet equinox 2.4 liter P0128 DTC engine time to temp too long

Michael Technician Massachusetts Posted   Latest   Edited  
Unsolved
Emissions
2012 Chevrolet Equinox LS 2.4L (K LEA Flex) 6-spd (6T45) — 2GNFLCEKXC6157468
P0128 — Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature),
Slow Warm Up

My 2012 Chevrolet Equinox 258,000 miles with 2.4 liter engine is setting a P0128 Engine time to temperature DTC. I have replaced the thermostat twice with an ACDELCO

thermostat from the dealership. I have also replaced the engine coolant temperature sensor With AC Delco part in the cylinder head next to the exhaust

manifold two weeks ago. Today I replaced the pigtail to ECT from the dealership with no apparent improvement. I let it idle for about ten minutes and then drove it about ten miles where the ECT on the scan tool showed 150 degrees F. When I got home it finally got to 220 degrees F while at idle. In total it takes 20 minutes to get to 195 degrees F and 23 minutes

until the coolant fan came on at 220 degrees F I am at a loss why this is happening. Any helpful suggestions would be appreciated. My Guess is the thermostat is staying closed too long. Also about a month ago I replaced the radiator and heater core with GM parts for preventative repairs. The heat works well in the vehicle.

Related Repair History

replaced thermostat twice with GM part. ECT replaced with ACdelco and GM/AC delco pigtail for ect.

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Helpful
Daniel Owner/Technician
Texas
Daniel Default
 

...I have had great results with Stant Thermostats for the last several decades...give one of those a try...Dan H. ...South Texas...

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Jeff Technician
Arizona
Jeff Default
 

Did you by chance change the heater hoses, I’ve seen several GM heater hoses that have restrictors in them. Also what is your ambient temperature ?

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Michael Technician
Massachusetts
Michael Default
 

Hello Jeff Florey. I did replace the heater hoses with GM parts. They did not have any visible restrictor. the ambient temp was about 40 degrees F.

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Jeff Technician
Arizona
Jeff Default
 

I would have to say that you have coolant flowing through the radiator all the time ,with that low ambient temperature it is cooling coolant. I would recommend a different brand of thermostat as Daniel said a stant unit.

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Michael Technician
Massachusetts
Michael Default
 

Hello Jeff Florey, I will verify the coolant temp with my fluke infra red probe and then change the thermostat to a stant brand part.

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Scott Mechanic
Arkansas
Scott Default
 

It's pretty easy to just feel the radiator hose on start up and see if it opens early. I'm sure you've been around long enough to know that. I'd try pinching off the heater hose. It seems like a stretch that 3 thermostats are bad. Maybe the new hose needed a restrictor on your application and didn't get one.

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Michael Technician
Massachusetts
Michael Default
 

Hi there Scott, Thank you very much for the feedback. Sometimes new does not mean good.

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Eric Instructor
California
Eric Default
   

This never happened before the radiator and heater core replacement? Is all the air out of the system? 220 at idle sounds high. Air won't heat the ECT sensor like coolant would.

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James Owner/Technician
California
James Default
 

I May just be tired, but isn’t the issuer slow warm up to temp? 23 minutes to get anywhere close to normal ? If I am reading this correctly, I would be suspicious of the stat not closing or opening way too soon. Wrong temp stat or cooling fans on too soon would be my first thought. Were the temps verified with an infrared tool?

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Michael Technician
Massachusetts
Michael Default
 

Hello James Callis, When I was monitoring the scan tool and watching when the Fan came on. The fan started at 220 degrees F and then dropped immediately to 208 degrees F and then settled down to 168 degrees F. I will use my Fluke 80t-ir/e infrared probe with my dvom next time I work on it.

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Gail Technician
North Carolina
Gail Default
 

I wouldn't think it would cool under 190 under any circumstance. Has the thermostat housing or water manifold been changed? Going from fan on temp (220ish) to 168* makes no sense. Not sure what i did to change the font mid sentence.

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Michael Technician
Massachusetts
Michael Default
 

Hello Gail Taylor, I have not replaced the thermostat housing or a water manifold. Several months ago I replaced the water pump assembly with a GM part as it was leaking at the weep hole. Thank you for the feedback.

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Michael Technician
Massachusetts
Michael Default
 

Hello Eric Zebe, The coolant temp issue has been an ongoing issue for several months. The IPC would show 1/3 on the temp gauge scale and then drop to zero. And then a few minutes later shows 1/3 scale. I used an Air lift to pull a vacuum and refill the system with new Dexcool and distilled water. The coolant level has stayed stable for a few thousand miles.

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Michael Technician
Massachusetts
Michael Default
 

Thank you Daniel for the Tip on Stant brand thermostats.

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Daniel Owner/Technician
Texas
Daniel Default
 

...I prefer to be called "Dan"....I requested that of management(Scott in particularly)...but my credit/debit card had "Daniel"...if they would be so kind as to allow me to be listed by my "preferred" name it would be GREAT !!!...Daniel is a bit formal and not what I'm used to...please consider granting my request to be called by DAN !!!...South Texas...

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Michael Technician
Massachusetts
Michael Default
 

Okay Dan sorry I will address you that way in the future.

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Daniel Owner/Technician
Texas
Daniel Default
 

...Wasn't about you addressing me that way....I was kinda hoping that DN Support would see it and change me to DAN...I can only hope...Dan H. ...South Texas...

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Cliff Diagnostician
California
Cliff Default
 

Interesting regarding your name. I am using my middle name because that's what I have been called by my family since I could remember. I am pretty sure this could be changed under profile settings.

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Daniel Owner/Technician
Texas
Daniel Default
 

...I sent DN Support a snail mail requesting a name adjustment...Dan H

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Steven Mechanic
Washington
Steven Default
 

I'm not familiar with GM vehicles, but does the auto. trans. cooler have a thermostat? Maybe it is stuck open.

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Michael Technician
Massachusetts
Michael Default
 

Hello Steven Mcgrew, The automatic transmission cooler is in the radiator and does not have a separate thermostat that I am aware of.

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Francisco Diagnostician
Virginia
Francisco Default
 

Have you checked for coolant leaks? I had one with the same issue and the solution was the water pump. It was leaking so little that no drops on the floor but enough to loose pressure and then take longer to warm up. Hope that helps you!!

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Michael Technician
Massachusetts
Michael Default
 

Hello Francisco Salazar, I have already replaced the water pump assembly with a GM part several months ago. That is a great tip thank you.

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Albin Diagnostician
Washington
Albin Default
 

If you suspect the thermostat leaking, you can test for the leakage right in the bay. With the engine cold, start it up and monitor the temperature of the top radiator hose, or the temp of the radiator core if it is accessible. I perchance the stat is leaking, the temperature of the hose, and or the radiator will start to rise soon after the engine start up. If the stat is sealing properly, the…

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Michael Technician
Massachusetts
Michael Default
 

Hello Albin Moore, That is a great tip I will try that one. Thank you.

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Rudy Owner/Technician
Nevada
Rudy Default
 

I had a similar situation with an hhr. Customer stated an mil condition with P0128. previous shop replaced ect sensor, pigtail, thermostat and engine control module. Even the bcm. I reprogrammed the ecm to current calibration, and monitored the temp and fan operation. To my surprise it would reach normal op temp and fan switched on at 217 and cooled down beyond Thermostat temp ! I was stumped at…

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Michael Technician
Massachusetts
Michael Default
 

Hello Rudy Cornejo, That is a great tip ! I would not have guessed that was an operating strategy of the vehicle.

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Caleb Diagnostician
Indiana
Caleb Default
 

Besides the fact that it sounds like the T stat is junk, do this. Pull the little 4 bolt cover off the timing cover an make sure the balance shaft chain isn't broke which also spins the water pump. Only takes 5 min.

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Michael Technician
Massachusetts
Michael Default
 

Hello Caleb Mohler, I agree the thermostat seems to be defective. I hardly ever have an issue with OEM replacement parts. If the balance shaft broke I would think there would be some huge noises coming from the engine compartment. Thank you for the Tips.

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Lesage Technician
Michigan
Lesage Default
 

If the Tstat was staying closed too long the temp. would've been higher. Is your ambiant temp. on the cooler side? 220 deg. before fan comes on is common on GMs. Are you missing some body shrouds in the front end? Bleed the system again

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Michael Technician
Massachusetts
Michael Default
 

Hello Lesage Diop, At the time of my testing it was about 40 degrees F outside. I have all factory shrouds in place. When I replace the thermostat I will vacuum bleed the system again with my air lift tool. Thank you.

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Geoff Diagnostician
Hawaii
Geoff Default
   

You would need to investigate this yourself, but I notice one of the re-flashes for that ECM is described as "New calibration increases robustness of environmental temperature model." Now, IDK WTH "environmental temperature model" means but it very well could be something/somehow related to warm-up speed. partial screen shot;

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Michael Technician
Massachusetts
Michael Default
 

Hello Geoff Welsh, Thank you very much for the help on a possible calibration update issue. I had not considered that.

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John Instructor
Pennsylvania
John Default
 

The code means that the PCM thinks the engine is staying cold too long. The description of the code is: "The ECM determines that the modeled engine coolant temperature has met the calibrated target of 198f and the actual temperature is less than 178f for 2 seconds or more". When you start the car note the engine coolant temperature, which after sitting long enough should closely match ambient…

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Michael Technician
Massachusetts
Michael Default
 

Hello John Gillespie, Thank you for your help. I do not have a thermal imager tool but I will use my infra red temp tool which i can use with my Fluke DVOM. I agree the thermostat is a problem and will get replaced. I heard from a GM tech I know and he said there have been some defective thermostats. I appreciate the clarification on the code set criteria. I will also reflash the pcm if…

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Edwin Mobile Technician
South Carolina
Edwin Default
 

Hi Mike. I hope your doing well. I had one of these issues awhile back. I believe if I can remember I did an ecm calibration update and it took care of it. Also if you have a thermal imager camera try using it and look for any signs of obstruction or basically look to see if the temp is uniform all through the system. Hope to see you at the big event this year.

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Michael Technician
Massachusetts
Michael Default
 

Hi There Edwin, Nice to hear from you. I only get to see you at the TST big event. I will be there at the big event as always. I will investigate the reflash you mentioned. I believe acdelco gets about 50 dollars per flash. I do not have a thermal imager tool but I do have a fluke infra red probe which I will use. Thank you, Mike

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Eric Owner/Technician
Wisconsin
Eric Default
 

After reading all the previous posts it looks like this problem may have started after you replaced the water pump. In the past I have had a few water pumps work too well and force the thermostat open. It makes for a difficult problem to solve and you have symptoms similar to what you are experiencing. The same testing applies, check the upper radiator hose temperature during warm up to verify…

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Scott Mechanic
Arkansas
Scott Default
 

I have to admit, too much pump would never occur to me. That would definitely have me pulling my hair out.

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Michael Technician
Massachusetts
Michael Default
 

Hello Scott Prowse, I too would have not thought a water pump would cause this sort of issue.

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Michael Technician
Massachusetts
Michael Default
   

Hello Eric Diedrick, Your feedback on the cooling system is pretty insightful. I had a few minutes to look at the car after work before it got dark outside. I used my infra red temp probe on the upper and lower hoses and heater hoses after driving it 30 minutes. The upper hose is 120 degrees F and the lower hose is 90 degrees F. The heater hoses were about 120 degrees F engine running. I am…

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Eric Owner/Technician
Wisconsin
Eric Default
 

Those temperatures are not hot enough. I would start with a replacement thermostat. I would heat the old new thermostat in a pan of water with a thermometer to see what temp it opens at. If it opens too soon then you will know it is a thermostat problem. If it opens at the correct temperature you will know you need to look elsewhere. I would test it at idle instead of driving, the slower engine…

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Michael Technician
Massachusetts
Michael Default
 

Hello Eric, I will test the current thermostat and the replacement in water increasing temperatures. I believe the heater hoses were basically the same temperatures. Thank you very much for you help.

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Scott Owner
California
Scott Default
 

Hi Mike, Ah, what used to be cut -n- dry, as in thermostats which used to fail by failing to open and caused overheating... Now 98% of the time on GM vehicles will open prematurely, or are stuck open causing this DTC to set. The other thing would be not getting to "X" Temperature used to be a good thing and guys would remove thermostats, or take a 195* out and put a 160* one in. A couple of…

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Michael Technician
Massachusetts
Michael Default
   

Hello Scott Chase, Thank you very much for the feedback. I have never had a cooling system fail in this way before. It is very perplexing to figure out. Why are the thermostats failing after a year or so in your experience? I will check ECT and IAT agree tomorrow morning before going to work. In general I have very good luck with oem parts and aftermarket parts not so much.

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Scott Owner
California
Scott Default
   

Hi Michael, I don't have the actual reason why GM thermostats do this, (or why they're problematic) but given my unscientific experiences, the stuck closed thermostats are relatively rare today. I'd have to say given the amount of P0128's that I see that this is something that is designed into the thermostats as some sort of fail safe, although Stant says it's not so -…

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Michael Technician
Massachusetts
Michael Default
 

Hello Scott Chase, I really appreciate the personal feedback on dealing with p0128 issues. Where the information listed for range 1 and range 2 thermostats? I do not recall reading about that in the GM Service information website on acedelcotechconnect​.​com I plan on replacing the thermostat this weekend. I am hoping that this will end the problem for me.

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Anthony Technical Support Specialist
Pennsylvania
Anthony Default
   

Hi Mike: Since I have a question, this is as good of a spot as any to ask. I didn't see if this is an electrically heated thermostat. Is it? Some vehicles in this group use them. BTW, I think this is what Scott was referring to (Page 45). gsi​.​ext​.​gm​.​com/gmspo/mode6/pd…​.​pdf Guido

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Martin Instructor
British Columbia
Martin Default
 

Hi Guido, that's just a basic mechanical thermostat in that one, same part # as in my wife's '15 Terrain, and my '03 Z24 commuter. Same thermostat as the one in the photo from my daughter's '05 Cavalier in my response to Scott above. FWIW, the electronic thermostat for a '14 Malibu 2.5L lists within about $2 CAD as the mechanical thermostat at approx $100 CAD. The last time I purchased an…

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Anthony Technical Support Specialist
Pennsylvania
Anthony Default
 

Hi Marty: Thanks for the feedback. It kind of reminds me of when I was a teenager. Someone asked how they could fit $15K worth of parts in a $5K car. Guido

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Martin Instructor
British Columbia
Martin Default
 

LOL Guido. That reminds me of the cost of a Kawasaki motorcycle in the 1970s that was possibly $2000, costing an estimated over $20,000 in replacement parts! Martin

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Michael Technician
Massachusetts
Michael Default
 

Hi Martin Smith, Thanks for the information on thermostats I appreciate it a lot.

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Martin Instructor
British Columbia
Martin Default
 

Hi Mike. You're welcome. FWIW, for all of the years I spent working in a dealership, I never had any issues with any OEM spec thermostat that I installed. However, given the silly price at my cost of about $62 CAD some years ago for that simple "mechanical" thermostat, I chose to install a Stant replacement for ~1/3 the cost and it worked just fine. I'd definitely take a good look at the…

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Michael Technician
Massachusetts
Michael Default
 

Hi Martin, Yes I will install a Stant thermostat this time.

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Scott Owner
California
Scott Default
 

Hi Martin, Here's a crazy example of pricing - diag​.​net/file/f6crrrdph… Part #21 is a bracket - … Care to hazard a guess on what that little piece of plastic runs? GM list is $74.41. I'm in the wrong business. BG

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Martin Instructor
British Columbia
Martin Default
 

It sure makes me wonder sometimes Scott. When the 2.5L engine was introduced a few years ago, there were some early production models with connecting rod knock and failures that resulted in damaged crankshafts. Until a new engine was available for training, we obtained two of the engines with bent forged steel crankshafts and subsequently replaced the cranks and bearings for ~$268 each!

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Rusty Owner/Technician
Massachusetts
Rusty Default
 

I’m late to the party here Mike but when I’ve suspected a leaking thermostat, I’ve clamped off the upper radiator hose to confirm that the ECT rises normally before removing and testing the thermostat in some water on the stove. Good luck

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Michael Technician
Massachusetts
Michael Default
 

Hey Rusty, Thanks for the great words of advise. I hope your family is doing well also.

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Michael Technician
Massachusetts
Michael Default
 

During a cold soak the IAT and ECT were within 1 degree of each other. My pressing issue is the automatic transmission has failed and I need now to decide on getting it rebuilt or replaced and reflashed. Murphy's law has been a difficult one for me this couple of weeks.

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Michael Technician
Massachusetts
Michael Default
 

The thermostat was replaced with a stant part. I works correctly now. The transaxle was replaced with a gm SRTA unit.

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