Engine Coolant Heater

[luap1980]

Is there a way to get the heater to work above 0 F/-18 C? Will my check engine light come on if I replace the plug? Why in the f**k did GM do this?

 

2008 GMC Sierra

All Terrain Crew Cab

5.3 liter

[minibike132]

mmmm maybe a little more info. What are you driving, what engine and what heater?

[minibike132]

sorry I obvously didn't look at the post title. Let me do a little checking and see what I can find. Anyone else chime on in.

[minibike132]

As far as I can tell the heater is not integrated into anything that would cause a check enging light. There isn't a diagram which leads me to believe its just the plug and the wire. You should be able to replace it. Also the manual says "to aid in 0 degrees or lower" That doesn't mean it only works in 0 or lower just that it's not really necessary. There doesn't look to be anything to inhibit operation above 0 it's just a poor choice of words on GM's part. If your looking to get instant heat thats not really what a heater is for its more for the engine fluids to maintain fluid status in real cold, with the heater on coolant isn't circulating so only the area around the plug stays hot. In order to keep all that coolant hot you would run up a million dollar electric bill. Thats just my opinion though.

[luap1980]

As far as I can tell the heater is not integrated into anything that would cause a check enging light. There isn't a diagram which leads me to believe its just the plug and the wire. You should be able to replace it. Also the manual says "to aid in 0 degrees or lower" That doesn't mean it only works in 0 or lower just that it's not really necessary. There doesn't look to be anything to inhibit operation above 0 it's just a poor choice of words on GM's part. If your looking to get instant heat thats not really what a heater is for its more for the engine fluids to maintain fluid status in real cold, with the heater on coolant isn't circulating so only the area around the plug stays hot. In order to keep all that coolant hot you would run up a million dollar electric bill. Thats just my opinion though.

 

There is a sticker on the cord itself which says operational below 0 F/-18 C. I have found out that there is a thermostat in the end of the plug that expands when it gets cold and contacts two wires. I beleive if I was to put a different plug end on and used the heater above 0 C/-18 F, I would get a check engine light. I beleive that there is a sensor on the engine that detects this, or so I have been told. Anybody have a solution? Is this the same for the diesel engine?

[Indy]

The diesel must be different. -18°C is awfully cold for a diesel to start without help.

[minibike132]

Sorry I can't find any documentation on it but I plug my diesel in at 35 and notice a reduction in glow plug warmup.

[GMCStepSide]

Yes, on the gas engines from 2005 and on, they have "tumor plug" on them that won't let current pass to the block heater until the temperature goes below zero. There is a huge thread about this from a couple years ago at http://www.gm-trucks.com/forums/index.php?...hl=block+heater

[minibike132]

Good find, I'm glad to see I'm not the only tech that looked like this when asked this question. I always forget to look here for previous posts. This is a good reason for the 5 post rule. Anyway I learned something new today. As I did yesterday and the day before. I'm here to learn as much as give help so thanks.

[GMCStepSide]

Don't feel too bad. Our local radio and television stations still broadcast ads "Plug in when it's below 20 degrees" for better air quality in the Anchorage bowl. Obviously they know nothing about the tumor plug and I'd be willing to bet 90% of those who purchased new GM vehicles since 2006 don't know it either. Poor folks...plugging their vehicles in like right now when it's 4 degrees outside thinking they're helping both their engine and the environment but really doing nothing for either. GM engineers and the EPA - what were they thinking?