ScannerDanner – How to test an electronic thermostat (GM design) part 1

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31 Responses

  1. This video will be a great re-enforcement of testing pulse width modulated output devices. Sorry it has been so long since my last upload, I've been busy on ScannerDanner Premium. 

  2. EzRepairs says:

    Hi scannerdaner, i work for a rental company and during the 2012/2013 chevy cruze wee had a lot of cars with this DTC, I always wondering what was the function and cause for this code as wee never got to work on this problem because the cars were steal under waranty, thanks for the video. Best teacher ever…

  3. Nick Nicu says:

    Thank you Paul! Great video as always! It's amazing the lengths car manufacturers go in the name of emissions. What was wrong with the plain old mechanical thermostat…?! You put an electrical circuit in there and guess what…?! That's the one that fails!

  4. This is a common setup on a lot Europe cars Bmw vw Audi Vauxhall all use some type of stat that does the same thing. It's to help the engine stay at a better temp so fuelling can be controlled better. An old type wax stat can have a 20 deg swing up or down so fuelling could be off a new type stat has poss only a 5 deg swing so engine runs at a more stable temp making fuelling more accurate. 

  5. Does those fault numbers have the same meaning what ever the make of the car is?

  6. Yes, fundamentals is key. I'm still waiting for the computer controlled "paint color" options. I do have some industrial equipment where the computer adjusts "actuator pressure" based on amount of current flow in the actuator circuit. I thought that was a rather cool concept. Fine instructional work Mr. Danner.

  7. happy543210 says:

    two year old car…shouldn't this repair be covered by the warranty?

  8. Lee Rattle says:

    Danner been busy wid his money making channel…lol..& us cheap skates have to wait for some more vids.  🙂 This stupid thermostat heater bs on a good percentage of 2006 on vehicles in UK , cus EU I suspect. Some even more complicated how they operate, on VAG vehicles they use rpm & temp open the stat,, what the hell was wrong with simple thermostat,. sigh


  10. steven yau says:

    could be the coil shorting the the housing
    or a cracked housing causing intermittent shorts to the coolant

  11. i just did one of these 3 days ago on a 2014! your way was alot better. what is your favorite brand of car to work on?

  12. the way the trouble tree is gm has you use a test light connected to the connector unhooked in both terminals of the connector command the thermostat on watrch and see if it turns on and off, if it does ohm out coil in thermostat. but your way is nicer keep up the good work 

  13. Bushougoma says:

    The component on the thermostat is called a bias heater.

    The biased thermostat must be for tighter emission control. A critical variable in emissions is engine temperature. How much of an improvement they're getting in emissions over a regulator thermostat I'd like to see. Or maybe they're just using it to get the engine warmed up and into closed loop quicker. A cold and warm engines emissions are night and day. Your guess is as good as mine.

    In any case this allows the PCM to accurately regulate the coolant temperature using the coolant temperature sensor as feedback.

    Gas clothes driers use a similar principle to avoid the cost of using 3 different bimetallic temperature switches for the different selectable temperatures (low, medium, and high).

    There is one temperature switch and a resistive heater is put into close contact with it. By placing a different resistor in series with the heater for each temperature setting the bias heaters temperature is controlled.

    By preheating the bimetallic switch it will open at a different temperature than it's rated for.

    The design on this vehicle is a slight variation using pulse width modulation to more accurately control the heater instead of a resistor.

    I've never seen one either but as soon as you said the word heater I knew what it did.

  14. Wael Ahmed says:

    Hi. BMW use same setup for years and always change thermostat for Same reason
    Thank you for your good job. 

  15. smitt9 says:

    This video will be a great re-enforcement of testing pulse width modulated output devices. Sorry it has been so long since my last upload, I've been busy on ScannerDanner Premium. 

  16. dynotec1 says:

    Danner, I have just discovered your channel and your approach to diagnostics and I have to say I'm completely blown away. I don't know if it's just me or what, but the way that you explain things and how you go about them is perfectly clear to me. I have been in the automotive repair industry for twenty years and I've sat in plenty of classes with some great instructors and you are at the top of your game. I'm in the process of watching all of your videos and I'm picking up great stuff in all of them. Thank you for sharing your craft! Bart

  17. douglas lee says:

    Here is another submission for the Suggestion Box. Perhaps you have addressed this in other video's, or on the Premium Channel, but I have not seen it myself. I apologize if you have already covered it.

    I am currently chasing a possible Key Off Drain on my 1999 Sebring JXi. I understand the principles of monitoring amperage, pulling fuses etc.

    However, yesterday I just came across information explaining that some  Modules can Stay Awake, and don't "Go to Sleep" for some period of time. I'm not referring to my car, just all cars in general.

    I am not able to find any information about the subject as it might apply to my car, including searching the FSM.

    SO, I am a little lost for information, so I am going to have to simply wait for some period of time (I'll probably aim for a half hour) before taking ABSOLUTE current flow measurements. I also want to avoid powering down the PCM, BCM, or TCM if I don't absolutely have to.

    SO, the idea for you is to perhaps do a video sometime and talk about how various Modules can sometimes stay awake, and the importance of knowing this before doing current flow testing (in series with battery) in analyzing current drains. If you have any knowledge about how long various types of modules (computers) might stay awake by type or by manufacturer, that would be a bonus.

    I know you are not an Electrical or Short Circuit Testing focused class, but knowing the fact that the PCM, TCM, BCM, etc can stay awake for a while sucking some degree of juice might be valuable to your viewers.

    Keep up the Great Work as always.


  18. steven males says:

    this is a nice little earner for gm £70,we have change a few of them, no need for this pointless thermostat ,  common in uk

  19. Looks like GM is still experimenting, being that the car is only 2 years old and had already failed. Typical GM bull. I had one of these things for a few weeks as a rental…was not impressed.

  20. Joe Chambers says:

    These are map controlled,some good info on the web,emailed you website addy with some info for you paul.

  21. Hey danner its Dustin get ahold of me have some questions 2774944 

  22. Rod X says:

    Many thanks for your videos. watching your vids has made me a better diagnostician. i have 4 local shops that bring me stuff they cant figure out, and i always succeed where they fail. Your basic methodology and grasp of theory and operation  based on circuit design (which i have learned as i see the advantage) makes diagnostics simpler. You turned me into a "scope guy". I am a better technician as a result. I still have to get my hands dirty turning wrenches, however i do get most of the electrical diag work, which suits me fine, and i make money on diag where many don't. Again thanks. keep em coming.

  23. Wow that is an excellent circuit description. Manufacturers are getting better with these flow charts.

  24. Mark Paynter says:

    Came across this in a BMW electronic thermostat, and one of the features I found out was to allow hotter running for emissions i general driving, and cooler running for high speed work

  25. Emin HVAC says:

    Outstanding work Danner. I stumbled on to you're channel by accident lol. I absolutely enjoy you're diagnostic skills. Thank you for the videos bud. Subd

  26. searcher68 says:

    Great vid Paul. Many thanks again as always. I actually broke one of these a couple of weeks ago on a 2010 Chevy Aveo while doing a cooling system flush. The thermostat looked removable from the housing, but as soon as I twisted it free I realized that the wires had broken. I had to eat the cost, of course, but I've been racking my brain trying to figure out how to do a flush without pulling the thermostat since it's all integral to its housing & electric heater. After watching your video I now know what I should have done, and am posting here not only to say thanks for another great video but also to share what I came up with. Since this is a pulse width modulated part, grounding the control side should force the thermostat to open, thereby enabling a good flush. I'll use a 'soft' ground of course by using my test light and this'll be my standard procedure in the future. Does this sound right to you?

  27. Juan Santos says:

    Just want to say that I have learned a lot from watching your videos. I tried my best to watch at least 2 videos a day, also I'm planning on buying your book. I just have a couple of questions about the Verus. Right now I have the Solus Ultra, and now I'm performing more diagnostic at my Job. Thinking of upgrading, and was wondering what is your review on the Verus, and is it as easy to use. thanks 

  28. adrian frias says:

    I heard you say that some viewers commented that your videos are too long. I want to affirm you on how informative your videos are. Appreciate you thought process and even your mistakes. If you made quick "pop tart" videos I would probably not view your videos. Please continue your hard work. Negative comments can be very discouraging and hinder progress. Just remember, it is a sign of trouble when everyone agrees with you. There would be no motivation to grow. Again thank you for your diligence to detail. 

  29. TTRVision says:

    there are cars with fully electronic thermostat control?  
    (direct drive valve on stepper electric motor).
    I assume that this could rise the cost of the unit but it will work and react very fast in maintaining the coolant temp….

  30. Recently my gfs car, opel astra j, which has same setup like you diagnose on tje video, got same problem. When dealer service adviser explain without proper explanation, i could not understand but now you explain everything. Thank you so much.

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