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Discussion Starter #1 (Edited)
The OEM oil pan heater on theCruze has a built in thermostat that keeps it from working at temps below 0F (-18C). This was done to keep the temperatures from interfering with the Engine Coolant Temperature sensor diagnostic that runs when the vehicle is started. There is some simple logic that attempts to detect block heater use but it is weak and easily fooled, hence the thermostat implementation.

This sucks for people who would like to make use of the heater to warm their engines in cold weather. 0F (-18C) is pretty cold, and though oil flow with the semi-synthetic GM Dexos oils may not be an issue at this temperature, cold start emissions and warm-up time certainly are.

Removing the thermostat will allow the oil pan heater to function regardless of ambient temperature whenever it is plugged in. I have only been using it this way for a few days and though I have yet to see any problems, that is no guarantee that problems will not show up. I will post follow up information if any issues arise.

The oil pan heater is only rated at 200w, so it is far from a powerful heater. Add to this the fact that it is just a steel heating element held against the side of the oil pan (limiting heat conductivity), and it really doesn't do a whole lot for the temperature of the engine when plugged in. It should keep oil flowing freely at extreme temperatures, though, making cold starts a little easier and less damaging to the engine.

BEFORE BEGINNING, READ CAREFULLY:

1. This may result in setting a P0116 code. Read up about this condition here, post 36 and 42:

http://www.gm-trucks.com/forums/index.php?showtopic=47527&st=30

2. Your oil pan heater cord is expensive to replace and this is a permanent modification requiring soldering to get it functional once the thermostat is removed.

3. You are modifying a 120V electrical circuit. Electric shock, short circuits, damage to your vehicle's electrical system, and FIRE are allrisks you need to fully understand before doing this yourself. Do not proceed with this unless you are comfortable. Do not blame me if this doesn't work out. YOU HAVE BEEN WARNED.

Step 1, pull the round plastic thermostat cap off using pliers and a back and forth rotating motion. I used a rag to keep from marking up the plastic. You will see the top of the thermostat. Using your pliers, gently pull the thermostat out while twisting back and forth. Doing this will permenently pull apart the crimped connections on the thermostat, so go slow and be patient, twisting and pulling gently until the contacts pull apart. You should have something like this when done:

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Now bend up the little tabs and solder a piece of 16ga (minimum) wire across the terminals:

208.jpg

Now push the cap back on using the pliers and rag. This will take a little effort and patience, just keep pushing and twisting, and you might have to push the rubber plug material up a bit also:

209.jpg

Once you're done it helps to check your work by plugging into a power meter to make sure everything is working OK:

210.jpg

This is what the bare heater looks like:

205.jpg

Good luck! I will follow up with any relevant information I discover regarding codes, warm up times etc.
 

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Discussion Starter #2
I updated the link to the GM Truck forum, it wasn't working properly.

For those interested, here's the condidions surrounding the P0116 code.

Running the DTC:
-Ignition is ON
-DTCs P0112, p0113, P0116, P0117, P0118, P0128, P0502, P0503 are not set
-Start up IAT (Intake Air Temperature) is greater than -7C (+20F)
-Engine is turned OFF for greater than 10 hours
-DTC P0116 runs once per drive cycle when the above conditions are met

Setting the DTC:
-Start up ECT (Engine Coolant Temperature) is greater then the IAT by more than 100C (180F)
OR
-Start up ECT is greater then the IAT by more than 15C (27F), then the vehicle is driven over 24 km/h (15 MPH) for 400 seconds, during which time the IAT does not fall by more than 8C (14F). If IAT falls more than 8C (14F) in that time, a block heater is detected and the test is aborted.
-DTC is set upon two consecutive drive cycle test failures

I'm not sure what happens after the DTC is set? Does the computer ignore the ECT sensor reading and go into some sort of limp mode? Does it soldier on using the values returned by the (apparently faulty) sensor? I'm not sure... perhaps a GM tech could look into this for us?
 

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Discussion Starter #3
UPDATE

Well, it's been over a week of plugging in my oil pan heater with bypassed thermostat, which means I've been using the heater at all temperatures, even well above -7C (20F) where GM's diagnostic will attempt to run the P0116 diagnostic. So far no issues, no codes, nothing abnormal.

Warm up times seem ever so slightly better, meaning the car still takes forever to warm up. Putting things into perspective, this is a small 200W heater secured to the side of the oil pan; it is not going to significantly heat the engine. It does, however, transfer a noticeable amount of heat into the oil pan. I can reach down behind the (ice cold) engine and put my hand on the oil pan right beside the block heater and it is warm to the touch. I have no doubt that this heater will perform well at its intended task, which is simply keeping the oil at a reasonable temperature for good engine starts.

We've had some BRUTALLY cold nights here in Ottawa lately, with a few getting below -30C (-22F), and my plugged in Eco MT has had absolutely no trouble starting. It cranks over with ease, fires immediately, and runs quiet and smooth right away with no ugly valvetrain noise. Electric power steering means no howling steering pump, either!

It was -24C this morning and another smooth quiet start.
 

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Discussion Starter #4
UPDATE

Well, it's been about a month of using the oil pan heater at all temperatures and no issues yet. This 200W heater seems, for now anyway, to be incapable of generating enough heat under the hood to affect the cold start diagnostics.

I'll update again if I find anything changes.
 

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Discussion Starter #5
UPDATE

I forgot to do an update on this thread in the spring. I pretty much used my oil pan heater right up until April when the outside temps were well above freezing and had absolutely no issues at all.

At this point I would feel confident recommending this for the owners of gas Cruzes. While it is still possible that a scenario exists that could trigger an engine code, I feel fairly confident that the little 200W oil pan heater just doesn't generate enough under-hood heat to affect any of the start up diagnostics.
 

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Discussion Starter #6
The OEM oil pan heater on theCruze has a built in thermostat that keeps it from working at temps below 0F (-18C).
I just realised a pretty severe typo... this should read that the thermostat keeps the heater from working until the temp drops below 0F (-18C)! :)
 

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Any updates for the brutally cold 2013-14 winter? How did the modified heater hold up?
 

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Thanks for the write-up. I was disappointed to find out my block heater only activated at 0 and below. Did this cord modification and now it's nice and warm for the cold morning starts up here in the mountains.
 

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Discussion Starter #9
Any updates for the brutally cold 2013-14 winter? How did the modified heater hold up?
Sorry for the terribly late response! The modification held up beautifully and through all the use I put it through I never got the car unhappy enough to throw a check engine light.

That certainly is not the case with my new 1400 W block heater set up, still working through some check engine light issues now that I'm adding some serious heat to the engine. When I do a full write up on that project I'll be sure to link to it here.
 

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Discussion Starter #10
Thanks for the write-up. I was disappointed to find out my block heater only activated at 0 and below. Did this cord modification and now it's nice and warm for the cold morning starts up here in the mountains.
Glad to hear it worked for you!
 

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Sorry for the terribly late response! The modification held up beautifully and through all the use I put it through I never got the car unhappy enough to throw a check engine light.

That certainly is not the case with my new 1400 W block heater set up, still working through some check engine light issues now that I'm adding some serious heat to the engine. When I do a full write up on that project I'll be sure to link to it here.
Glad to hear you're still trying the block heater setup. I went ahead and installed OEM Aftermarket Heated Seats, and they work quite well. A How-To is posted in the Interior Section.

I'd be interested to hear how the block heater is working out, and I look forward to your post.
 

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Discussion Starter #12
I'd be interested to hear how the block heater is working out, and I look forward to your post.
The heater itself is working quite well, it's just the darn codes it's setting off... the same ones I was worried about when modifying the stock oil pan heater cord, which were never an issue until I got much more serious with the heat.

Update soon, I promise!
 

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The heater itself is working quite well, it's just the darn codes it's setting off... the same ones I was worried about when modifying the stock oil pan heater cord, which were never an issue until I got much more serious with the heat.

Update soon, I promise!
Looking forward to the update. I never did get around to modifying my cord - still on the list of things to do
 

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Can you explain how this oils pan heater works? Is it plugged into a wall outlet or something? How is it getting 120v?
 

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Discussion Starter #15
Yes, it plugs into an extension cord to get 120V. It is optional as well, not every Cruze will have it. If you're does you should find the cord and plug near the air filter housing under the hood.
 

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I simply exchanged the original cord with one off another vehicle in my driveway that does not need the heater readily available and does not have a thermostat. Great that they are all GM products with the round two prong connection as standard format.

I am not worried about engine codes. I can reset them on the fly at anytime, but something makes me think that is will only activate the codes if it detects conflicting temperatures during two successive heated engine starts with enough elapsed time between each. I suspect that I will not have that problem because I heat the car in the morning and drive to work and 8 plus hours later when I leave work after sitting cold.

Has anybody ever tracked and monitored the effectiveness of the oil pan heater? If not, I hope to collect data on the heating curve over several hours. It should eventually flatline when the engine and engine bay heatloss rate equals the 200 watts energy heat in. How much heat energy actually gets to the engine and coolant?

I intend to log the following items, engine oil temp, intake air temp, ambient air temp, and engine coolant temp. Thankfully I should be able to log the information with the key off, I believe that gm keeps the OBDII connection constantly live.

I also intend to do a cold engine idle warmup logging and a heated engine warmup to 80 degrees ECT. I am willing to sacrifice a few cents of gas for science.

Anything else you thing will be useful or available to monitor?

other things to think about....

1. The key thing about heating the engine a quick as possible it to get the fuel management system to closed loop as quick as possible. I had one car do it in a few seconds no matter how warm the engine was. My initial assessment of my Cruze looks like around 60 seconds from cold when lamda climbs up to 1 for stoichiometry, but might be under light load, (I don't idle my car very long). looks like 10 seconds for a warm or hot engine. Damm something else to analyse...

2. Heat loss to atmosphere will eventually equal heat input, which is great if you want to melt the snow off the hood of the car but here on the east coast of Canada electrical power is 14.947 cents a kilowatt and becomes energy wasteful. Gas will be around 120 cents a liter by tomorrow therefore my fuel savings will have to be around 1/8 of a liter per kw or better per engine warmup cycle.

3. I was kicking around the idea of getting a circulating engine heater, but I suspect that it will take a longtime to recover the expenses back on speculated fuel savings alone. However my car takes a longtime to heatup mostly due to my light drive before I get to the highway depending on route.
 

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Discussion Starter #17
...something makes me think that is will only activate the codes if it detects conflicting temperatures during two successive heated engine starts with enough elapsed time between each. I suspect that I will not have that problem because I heat the car in the morning and drive to work and 8 plus hours later when I leave work after sitting cold.
This is true, and is exactly what I've found in my daily driving. As long as I let the car sit for 8 hours at work without being started I avoid setting codes. The startup diagnostics need to see a "test fail" on two consecutive starts with at least 8 hours of rest in between ignition cycles.

Has anybody ever tracked and monitored the effectiveness of the oil pan heater? If not, I hope to collect data on the heating curve over several hours. It should eventually flatline when the engine and engine bay heatloss rate equals the 200 watts energy heat in. How much heat energy actually gets to the engine and coolant?
It's actually surprising how much heat gets into the engine, those guys at GM know what they're doing. That tiny little 200W heater gets the whole front cover and crank pulley area nice and warm to the touch, right where the heat needs to be to ensure easy cold weather starts. With the heater going the engine fires up like it's a nice spring day, even when its -20C.

I took the OE heater one step further by insulating it on the back and sides with RTV silicone sealant. I also replaced the original thermal grease with stuff meant for computer CPU coolers in case the OE stuff didn't work well. It made a noticeable difference in how warm the oil pan was on either side of the heater, and I can hold my hand on the heater now without burning it.

Having said that, it doesn't preheat the engine to the point of getting instant heat from the heater, but the coolant temp gauge jumps off the stop much sooner after setting out.

I intend to log the following items, engine oil temp, intake air temp, ambient air temp, and engine coolant temp...
...Anything else you thing will be useful or available to monitor?
Sounds like a pretty good approach! The more geek you throw at it the better!

I was kicking around the idea of getting a circulating engine heater, but I suspect that it will take a longtime to recover the expenses back on speculated fuel savings alone. However my car takes a longtime to heatup mostly due to my light drive before I get to the highway depending on route.
I now have a custom circulating heater setup with a 1000W tank style thermosyphon heater and a 12V Prius electric water pump to circulate coolant. It works pretty well and usually has the coolant above the 50C gauge stop even on cold mornings.

I need to do a full write-up but wanted to get all the details with the codes figured out beforehand. I have a feeling I will end up tuning the codes out with HPTuners, I'm not sure there will be a mechanical way to get around it. For the record I never had an issue with codes using the OEM heater, even after removing the thermostat, no matter what the weather was. It just doesn't heat things up to confuse the diagnostics. The 1000W heater + oil pan heater(s) easily messes with things. :)
 

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Did you canablize a Prius to get that Electric Water Pump to circulate the Coolant ? If yes Cool Beans .
 
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Well this could prove interesting enough for some real attention, and you have managed to add some ideas that even my technical mind had though about before on the Pontiac Vibe that I could apply on the Cruze. Just so that you know, I grew up in the Navy as an weapon systems electronic/mechanical technican and after 23 years of service I get to watch other technicians work and coordinate system trials on ships as a chief.

I will work on a methodical plan and data collect all the information available on the ECU. For now I will blog it, but will assemble an organized document maybe worthy of publication.

I used copper antiseize compound on the Pontiac Vibe engine which used a dry cartridge blockheater which was installed in a cavity on the block, and was thinking about applying a layer of marine high temperature insolation on the outside of the block adjacent to the blockheater. I think I will do the same for this car which in my mind will be easier as it is on the open access to the oil pan.

Your install of the circulation heater sounds great... I will get there eventually, I only have 2k on the car give me a few months and I will be able to mod the car once the warranty worry has elapsed.

Got the cold idle warm up done today to 80 degrees C, great for the fact that is was -10 C.

I will continue to blog here as I get the information sorted out, unless there is a sharepoint location to assemble the information for discussion.
 
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