Don't really need the block heater here but was wondering if it would help it warm up faster. I only drive 6 miles to work in the mornings and the truck is just getting up to temp. If I plug in the block heater will it come up to temp quicker so engine is more efficient and my feet stay a little warmer? Temps here has been in the 20's at night with it dropping into the teens in late Dec and January. Rarely does it get below 0.

Don't really need the block heater here but was wondering if it would help it warm up faster. I only drive 6 miles to work in the mornings and the truck is just getting up to temp. If I plug in the block heater will it come up to temp quicker so engine is more efficient and my feet stay a little warmer? Temps here has been in the 20's at night with it dropping into the teens in late Dec and January. Rarely does it get below 0.
The last three nights here have been -3, 4 & 0, plugged the block heater in at 4:00am for use at 7:30am. The major difference is that the glow plug light comes on and goes off so quick it is hard to see. The engine temp comes to 160deg (just off the peg) within a couple of minutes, but getting it above that requires driving it. Even with the elevated idle the heater temp is just luke warm until the truck is driven.
My thoughts are that the advantage is that the engine, batteries and starter will see increased life due to a warmer/easier start and does not require a very long idling period. I dont plan on using the block heater except when temps get below 10deg.:rolleyes:

If you are going to use a block heater consider putting a $8.00 timer on the extention cord and setting It to go on 2 hours before you go to work, it will make a world of difference.

Personally I Dont like using block heaters above 32F.

good luck

I have not seen the setup for the D-Max. How hard would it be to install the oem block heater? This last week of cold temps has really got me thinking about installing one.

Thanks in advance

IIRC, all Duramax equipped vehciles come with the block heater as standard equipment. You just have to search for the cord. You will find it tied up on the passenger side of the engine compartment, near the fuel filter.

Thanks everyone. May try it a couple times to see what happens. It's the only thing on my truck I haven't played with yet.

My block heater cord was tied to the battery cables from the passenger side cable down near the plastic fender insert.

In cold climates, it will greatly reduce the wear on your engine. 90% of all engine wear occurs at startup.

The problem with my block heater is the cord seems to be to short to reach out the front of the grill. I have it zip tieded in my passenger side wheel well. Just not as convenient as if it could be out the grill. Any suggestions:)

Does it hurt anything to use it when it isn't that cold?

The problem with my block heater is the cord seems to be to short to reach out the front of the grill. I have it zip tieded in my passenger side wheel well. Just not as convenient as if it could be out the grill. Any suggestions:)
Pull the cord out of the wire loom that it is in, you can gain about 2 feet doing this. You can then route it up to the front bumber and out the hole for the tow hook or some other place if you like.

Pulled mine out last night and zip tied it to the tow hook. Of course now the weather has warmed back up, only into the mid 30's last night. Oh well, at least now I have it out where I can reach it and won't be out there when it is 10 degrees and blowing snow trying to route it.

Using the block heater when it is too "warm" can set a P0181 code especially if the grille blanket is used. To keep the engine light off, I wouldn't plug in the heater until it gets down to about 20 degrees.

I have pics on my web site under Tech tips showing where the cord is tied. Same deal on the 2005's.

my block heater cord is in the engine compartment near the battery. anyone know if it can be rerouted down through the grill, or should I get a short extension cord to do this?
on an urelated matter, are air & oil filters for a 2004 Duramax the same as the 2005? thanks.

Please tell me I didn't screw up. From what I'm reading here, I shouldn't be pluging in my truck and leaving it in all night. I'm a volunteer fireman and sometime get called out in the middle of the night. I thought I could just plug it in and leave it. There are times I don't use the truck till noon or later and the outside temp has risen above the freezing mark. Is this a BAD thing to do. This is my first diesel and I'm still learning. Thank GOD for this site or us newbies would be SOL!!!

I have taken to not plugging it in unless it is going to be real cold when I get in. (<20) Even then, the Dmax starts right up. This morning it was 25 degrees and not a problem. In PGH, you generally don't need it very often. My old 6.5TD was another matter.....

Im also in the same boat as Pgh and get calls in the middle of the night. What I think Pgh is trying to get across is that our normal response to the firehouse is about one mile or less. So what is worse. Dog a cold engine or leave it plugged all night.

my block heater cord is in the engine compartment near the battery. anyone know if it can be rerouted down through the grill, or should I get a short extension cord to do this?
on an urelated matter, are air & oil filters for a 2004 Duramax the same as the 2005? thanks.I pulled mine out of the wire conduit and its plenty long enough to bring it out of the oval holes in your bumper, you can gain about 2 foot buy doing this.Plus when you pull it out of the conduit your pulling it out towards the front of the truck, I did this and have more then enough cord to plug in.

Hey Harley,
Get yourself a 5 ft extension cord and have that hanging out the front and plug your block heater into it, then tie wrap everthing nice and neat under the hood. I use this method with two 5 ft cords because I also have two battery warmers as well as the block heater and it looks real neat out front and under the hood.

Using the block heater when it is too "warm" can set a P0181 code especially if the grille blanket is used. To keep the engine light off, I wouldn't plug in the heater until it gets down to about 20 degrees.Just curious but, how do the use of the block heater affect setting any type of engine code, regardless of outside temperature or the use of the cold front blanket?:eek:

I know of a transit company that instructs their drivers to use the block heater on their buses when the temperature is below 40 degrees.

My better half’s shift ends at 4 pm. and the block heater on her bus is plugged in from 4 pm. until 7:40 am, when her shift began the next day.

Of course they are using Censored fordsCensored . So far, my Durmax starts just as easy on a cold morning, as my old 350 chevy, maybe even quicker.:rolleyes:

There is another thread about the P0181 code.

What it comes down to is the Dmax simply does not "need" to be plugged in. Many of the larger diesels do not have glow plugs or common rail injection, and thus are much more suseptable to hard cold weather starts.

GM doesnt recommend plugging in the block heater above 0 , only to use it on temps below 0 degrees.Remember vehicles dont feel wind chill.

There is another thread about the P0181 code.

What it comes down to is the Dmax simply does not "need" to be plugged in. Many of the larger diesels do not have glow plugs or common rail injection, and thus are much more suseptable to hard cold weather starts.The buses that she drive are of the F350-F450s, which have comprable engines with our Durmax and they do not start as well as our Duramax . . . and I agree that Dmax does not need to be plugged in but, what would it hurt if you did, that is my question. What harm is done?:rolleyes:

Remember vehicles dont feel wind chill.:confused:

There is no actual physical harm plugging in the heater, to answer your question. You *might* throw a code.

The problem with my block heater is the cord seems to be to short to reach out the front of the grill. I have it zip tieded in my passenger side wheel well. Just not as convenient as if it could be out the grill. Any suggestions:)
I just pulled mine other day. After you remove cord/conduit from clip on fender wall, carefully cut tape to open conduit. There were 2 zip ties that need to be cut. Remove all of the tape to separate plug wire from harness. I routed mine and zip tied so I can access through p.s. bumper air flow hole.

There is no actual physical harm plugging in the heater, to answer your question. You *might* throw a code.

Exactly what I thought, I read dmaxallitech post about the computer gets confused because of the water temperature being higher than the intake air temperate which confuses me. Because, normal operating temperature the water temperature is higher than air intake always and how about thirty minutes or a couple hour shut downs the water temperature don’t cool off that much. However, I am not a tech and trying to learn as much as, I can about my truck. I think I am going to hook up my block heater and see what happens. I have been using a cold front since the outside temperature has been 50 and below. Over the holidays I took an 800-mile trip and never removed the cold front without setting a code or any over heating. I plan to tow about 9200 next weekend therefore; I will remove the cold front while towing.
Thanks for the information.:)

I plug mine in every night, whether it's in the 40s or 20s. Not so much for cold starts in the morning (it starts fine with or without it) - but it's nice to have the coolant at 110 degrees vs. 45. I get heat in the cab much sooner than when I don't use the block heater. I plug it in when I get home from work at 7pm, and unplug it the next morning when I leave at 8am. It's just a heating element... you're not going to hurt anything, aside from maybe your electric bill ;)

The ECM does a check of the temp sensors once during a cold start up. Cold start is after the ECM determines that the engine has been shut down for 10 hours or more. The ECM also checks to see if the block heater was plugged in by comparing the start up air temperature with the air temperature after driving over 15 mph for 400 seconds. If the Intake Air temperature drops by more than 10 degrees, then the ECM determines the block heater was used and doesn't run the temperature comparison test. If it drops less than 10 degrees, then the ECM looks at the coolant and fuel temperature. If there is more than 18 degress differance between the fuel temperature and the coolant temperature, the code (P0181) is set.

So the problem is that when it is warm outside, and the block heater is plugged in the coolant temperature is much more than 18 degrees hotter than the fuel, but the intake air temperature doesn't drop far enough and fast enough for the ECM to realize that the heater was plugged in.

I plug mine in every night, whether it's in the 40s or 20s. Not so much for cold starts in the morning (it starts fine with or without it) - but it's nice to have the coolant at 110 degrees vs. 45. I get heat in the cab much sooner than when I don't use the block heater. I plug it in when I get home from work at 7pm, and unplug it the next morning when I leave at 8am. It's just a heating element... you're not going to hurt anything, aside from maybe your electric bill


I agree with you wholeheartedly! I will start using my block heater this week because, I live in a small town and my engine does not get a chance to warm up on the short trip around town and back home.
I believe a warm engine is better than driving a cold engine although, I do believe my electric bill is going to increase.

The ECM does a check of the temp sensors once during a cold start up. Cold start is after the ECM determines that the engine has been shut down for 10 hours or more. The ECM also checks to see if the block heater was plugged in by comparing the start up air temperature with the air temperature after driving over 15 mph for 400 seconds. If the Intake Air temperature drops by more than 10 degrees, then the ECM determines the block heater was used and doesn't run the temperature comparison test. If it drops less than 10 degrees, then the ECM looks at the coolant and fuel temperature. If there is more than 18 degress differance between the fuel temperature and the coolant temperature, the code (P0181) is set.

So the problem is that when it is warm outside, and the block heater is plugged in the coolant temperature is much more than 18 degrees hotter than the fuel, but the intake air temperature doesn't drop far enough and fast enough for the ECM to realize that the heater was plugged in.Interesting, when i plugged my 05 in for the first time all night it threw three codes on the THIRD start that day and on the second start it started in "cold mode" (ie. glow plugs were on for max time and it rev to like 800 for about 15 or 20 seconds). The three codes were some thing with fuel temp, coolant temp and turbo underboost. It wasnt really all that cold when i plugged it in, i was more just testing the block heater to see what it would do. Took it to the dealer and they reset the codes and didnt really do anything else. Im guessing that was realated to this problem. It had me confused, but it didnt happen again so i wasnt that worried about it. I think this is what it was.

Damn these trucks are smart ):h . I guess thats a bad thing sometimes

My 2 cents on the block heater - plug it in when the temp is 40 or below, use a wall timer to run it only a couple of hours, and enjoy a warm truck quickly after starting it! It's better for your engine too. Mine runs 3:30 to 6:30 AM every night.

Got the front covers on too. Keeps the engine up around 210 when driving. Not only better for your engine but also slightly better on fuel mileage.

I 'discovered' the P0181 code this morning... Not sure but if DMax is checking air temp, if its using the same thing my mirror does I know it's getting a screwy reading. With the winter cover on it is now enlosed by the radiator and sometimes reads almost 80 when it's 35 degrees out!!! Nice design huh?

Tonight I'm going to see if moving the sensor down by the tow hook will get rid of the P0181's. But I'm not stopping pluggin' it in.

Intake air temp sensor is in combination with the MAF on the intake tube just after the filter.

Thanks Fingers. I was afraid I was (wrongly) confusing the outside temp sensor and air intake sensor. Ok, well I'll get a better outside temp read anyway! I moved it tonight, wired tied it down behind the bumper, went for a ride (any excuse) and the temp was accurate.

Thanks for the information.

You paid for it so you might as well use it. It is so much easier on the engine to start warm and it only costs pennies. I would always plug my cat in below 35 degrees. The engine will apreciate it when it gets older....I PROMISE.
My first cat i sold had 850000 miles and the 2nd one had 565000 miles.
plugging in is a good habit to get in to.AND IT DOESN"T HURT

Harley99
What I did was remove some of the cord from the bundle of wires. I went to Advance and purchased some wire protector and rerouted the cord up front and attatched it to the tow hook with zip ties. I use it when it drops below 20 only because it is there, and I agree most damage is done at startup. I only plug it in for a few hours instead of what the book says (minimum of 8 hours) I personally dissagree with that.

harley, i sliced the black plastic wire loom which houses the block heater cord and battery cable, which allowed more than enough slack to wire tie the end of the cord to the tow hook in the front bumper.