Engine Hot Light

riverwarrior2010, You get the light off by repairing the problem that caused the light to come on in the first place. Simply shutting off the check engine light is not a repair. Even with the light off the error will continue to be stored in the trucks PCM. Your trucks PCM is storing at least one error code that's why the light is on in the first place. You need to have the codes read to determine what the problem is so it can be fixed. Auto Zone will read the codes for you for free. Have a scan done at any Auto Zone store and write the error codes down so you don't forget them. Then post the codes here on the forum so that the pros here can see them and they will tell you how to fix the problem.

temp sensor should trigger a code but changing it may fix the problem and not too expensive

River,

I agree with Jerry on the temp sensor, but hold off on replacin it for now. Are you runnin Dexcool antifreeze? If you are then that's your problem, along with the possibility of an air pocket in the cooling system. Go to a quality auto parts store and buy a Prestone Flush and Fill Kit. The kit is designed to be permanently installed on the truck, and will get rid of any pockets. It simplifies flushing the system and any future flush jobs. Make sure you install and use the kit via the enclosed instructions. As far as what antifreeze to use? Use only the one that appears in the link below.

http://www.peakauto.com/antifreeze-peak-global_lifetime.shtml

ok 409 / anti dexcool?? / why does gm say use only dexcool and you say never use it? i've investigate the pros and cons online and none are as negative about it. just wondering what your findings are and problems you've had with it. i have two gm cars that are over 100000 and run fine on it.

There is remarkably little difference between the green antifreeze and DexCool. Both are ethylene glycol-based. Both require a 50/50 mix with distilled water. GM claims tap water is suitable for DexCool, but why introduce unnecessary minerals to your engine? The differences rest in the type of corrosion protection each product offers. Green coolant uses a silicate-based corrosion inhibitor that coats the metal. Over time, these inhibitors break down, requiring a coolant flush every 30k miles or so. In an aluminum engine, green coolant does not change color when it breaks down; so many owners have no idea when this has actually occurred until their nice expensive aluminum heads have cracked. In an iron block engine, green coolant will turn reddish-brown with rust when its corrosion inhibitors break down. DexCool (phased in by GM during the 1995 model year), on the other hand, uses an acidic (GM calls it “organic”) corrosion inhibitor that does not break down over time. However, DexCool does not coat metal components as much as green coolant does, so proper levels must be maintained to ensure corrosion protection. Because corrosion protection does not diminish over time with DexCool, it can be left in the engine much longer than green coolant. While it's disputable whether or not you should leave DexCool in for the 150k miles that GM & Texaco claim, DexCool should easily be able to stay in the engine for 75k miles, two and a half times that of the green coolant. 75k miles is generally what the average vehicle travels in 5 years, and GM does not recommend leaving DexCool in for longer than 5 years

River,

Glad to hear the problem fixed itself. Doesn't happen often enough in this business but it does happen, and when it does that's a good thing :-). Right now I'm responding to the question you asked earlier, appears below for your convenience?

ok 409 / anti dexcool??

Well man, apparently you're not aware of the Class Action Law Suit against GM regarding Dexcool. Here are just a few links on the lawsuit. If you simply go to Google and type in Dexcool Law Suit you should get over a million hits. The basis for the lawsuit is the damage and in countless cases the (destruction)that Dexcool does.

http://www.topix.com/forum/autos/TMEUDCQK02ML7UKH4

http://www.leftlanenews.com/old-gm-settles-lawsuit-with-dex-cool-owners.html

http://www.gohtsn.com/article_860.shtml

Jerry,

You asked about the Dexcool and why GM recommends it. My opinion is that they spent lots of money formulating it and reformulating it and they probably don't want egg on their face. You also might want to consider planned obsolesence. If you can get the cars to run long enough to go past the warranty (shouldn't be all that hard) and then keep the dealer service and parts sales up after the warranty... Naw! What am I saying? A "reputable" company like GM would NEVER do that. Shame on me! :-)

My personal experience (and would venture to guess that it's Big Block's as well) is that I have replaced more gaskets, water pumps, radiators, etc. on GM vehicles (since Dexcool) than ever before. I wouldn't recommend the stuff to anyone but it sure appears to have made me lots of money.

The link below might be interesting to you. I'm not saying that you can believe everything you read (including a corporate giants recommendation) but I thought it made for good reading.

http://www.dex-cool.net/

Also you will notice that Block didn't recommend the old school "green" in his link.

Hope it helps. Thanks.

Drive,

(You said) Also you will notice that Block didn't recommend the old school "green" in his link.

Good point buddy and thanks for sayin it man, but colors don't mean anything anymore. You know me, and how I write and how I post when it comes to cooling systems problems like this. Always use a Prestone Flush and Fill Kit and use only the antifreeze in the link below.

http://www.peakauto.com/antifreeze-peak-global_lifetime.shtml

Why?
Simple.

Both the antifreeze and kit work the first time right out of the package.

Block,

I mentioned that to be SURE that Jerry and other readers/contributors understood that the old school "green" was not what you were recommmending as a replacement for Dexcool.

While I've got your attention, what's your opinion on Valvoline products (including coolant)?

Drive,

Valvoline oil products are ok, but I've been usin Castrol for decades, and don't see any reason for changin. Valvoline coolant and Zerex are the same thing. Used to use Zerex, but switched to Peak Global because, back in the day one of my customers was a sales rep for Peak. She hooked me up and I was gettin a great price on the stuff. Started usin it, liked it, saw that it lasted longer than Zerex, so I never went back to Zerex.

409 / drive - even if dexcool, isn't cool, your opinions are. they key here is changing fluids earlier than most people do. i've found the old fram advertisement is so true, "pay me now or pay me later"

Jerry,

(You said) pay me now or pay me later

That's right buddy, and that's why you shouldn't believe anyone who tells you the 3000 mile changin your oil and filter rule is dead. It's not dead man, and it's more alive today than it ever was, because of the garbage engines that are rollin outa Detroit these days. Wanna use dexcool? ok you can, you just gotta remember to change it every 6 months. Take care man :-).

Jerry,

"pay me now or pay me later"

You better believe it my friend. These companies extending the service intervals to keep "annual maintenance costs" down so they look good on paper really grind on my nerves. The problem I have with it is that the consumer suffers the consequences while the dealership parts and service departments thrive from the failures occuring just outside of warranty. Like I said before, it seems to be good for business and I've made lots of money as a result of their tactics but the average Joe loses. The sad thing is how hard it is to get some people to believe that their freakin POS Jaguar (my opinion) needs an oil change more often than once a year or 10,000 mi. BRAINWASHED! My regulars know that I'm truly looking out for their best interst but some folks are just sure that the manufacturer knows best. For those that can't see the light I just smile and welcome them back. I'd prefer to make the money on the maintenance end but I'll be glad to take it on repairs. THEIR CALL!

I have had the same problem with the engine hot / ac turned off problem. It started about 6 months ago and when it was cold in the mornings. It would sometime come back on and sometimes not. I got to where I was disconnecting the battery and reseting alarm which would last about 3 or 4 days and then return. Finally changed out temp sensor and it quit for about 3-4 months and now it is back again. Ready to try about anything. Thermostat or coolant etc..
Contacted GM and they never heard of this problem, it it literally all over the internet with little or no solution. There are more answers here than anywhere else.
No codes came up on auto zone check either.

tlba, sometimes a new part is bad and if it fixed the problem before its not that expensive to see if a new one, maybe from gm, would solve it.

tiba,

Moral of the story is that Dexcool SUCKS. If you're gonna use it remember to flush it every 9 months. Longer than 9 months? Well, it's gonna break down and cause damage. You're far better off usin the product in the link below.

http://www.peakauto.com/antifreeze-peak-global_lifetime.shtml