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I have a 2011 LML which I purchased used last year. The truck currently has 55,000 miles on it. Since owning it, I have had 3 separate issues with the glow plugs. I will get a CEL with the Code "Cylinder X Glow Plug Control Circuit" (X representing whatever cylinder it is). I have had issues with the #8 and #7 glow plug and today I got a code for the #6 one. Looking back at the GM Service Records for my truck, it appears as if the previous owner also had a number of issues with the glow plugs, the first being reported when the truck only had 1,000 miles on it! Every time there is a problem, the dealer just throws glow plugs in it and gives it back. According to the service records, the GP Controller was replaced at one point before I owned the truck. My major concern (aside from it being an inconvenience to keep going back to the dealer) is that my Powertrain Warranty is up in January and what is going to happen when I get stuck footing the bill for this every few months? Is this a known problem with the LML motors? Are there any TSBs out there regarding it? Is it worth my time to try and contact GM and above the dealer level and see if they will do anything? Thanks for the info!
 

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Make sure both batteries are in good condition. Glow plugs, at least in cold weather, require good voltage.

Here is info from ALLDATADIY relating to my 2008 model. You may find something of help in this:

Glow Plug System Description

In the diesel engine, air alone is compressed in the cylinder. Then, after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs, due to the heat of compression. Eight glow plugs are used as an aid to starting.

Control of the instant start system (ISS) glow plugs is accomplished by a glow control module unit and 4.7 volt glow plugs, requiring 2 seconds to heat up to 1,000°C (1,832°F). The temperature and the power consumption is controlled between the engine control module (ECM) and the controller within a wide range to suit the engine's pre-heating requirements. Each glow plug is energized individually. This capability yields more optimum heat times for the glow plugs, thus pre-glow times can be kept to a minimum for short wait to crank times and maximum glow plug durability. A DTC will set if there is a glow plug system fault.

A normal functioning system operates as follows:



  • Turn the ignition ON with the engine OFF, and at room temperature.
  • The glow plugs turn ON and heat up in 2 seconds and then are pulse-width modulated (PWM) for another 2 seconds.
  • The glow plug wait lamp is ON for 1 second during cold start.
  • The glow plug wait lamp may not illuminate during a warm engine start.
  • If the engine is cranked during or after the above sequence, the glow plugs may cycle ON and OFF after the ignition switch is returned from the start position, whether the engine starts or not. The engine does not have to be running to terminate the glow plug cycling.
The glow plug initial ON time will vary based on the system voltage and temperature. Lower temperatures cause longer ON times.

The ECM provides glow plug operation after starting a cold engine. This post-start operation is initiated when the ignition switch is returned to Run, from the Start position. This function helps clean up excessive white smoke and/or poor idle quality after starting.

Glow Plugs

The glow plugs are 4.7 volt heaters in each of the cylinders that turn ON, then pulse-width modulated when the ignition switch is turned to the RUN position prior to starting the engine. They remain pulsing a short time after starting, then they are turned OFF.

A Wait to Start lamp on the instrument panel provides information on engine starting conditions. The Wait to Start lamp will not illuminate during post-start glow plug operation.

Glow Plug/Controller

The glow plug controller is a solid state device which operates the glow plugs. The glow plug controller is connected to the following circuits:



  • The fuel heater ignition 1 voltage circuit
  • The battery voltage circuit
  • The CAN communication circuit located between the engine control module (ECM) and the glow plug controller
  • The engine ground circuit
  • The glow plug supply voltage circuits located between the glow plug controller and the glow plugs.
The glow plug diagnostic circuits are directly monitored individually by using a separate transistor to control current to each glow plug. Individual diagnosis is thus possible for every glow plug.
 

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I have a 2011 LML which I purchased used last year. The truck currently has 55,000 miles on it. Since owning it, I have had 3 separate issues with the glow plugs. I will get a CEL with the Code "Cylinder X Glow Plug Control Circuit" (X representing whatever cylinder it is). I have had issues with the #8 and #7 glow plug and today I got a code for the #6 one. Looking back at the GM Service Records for my truck, it appears as if the previous owner also had a number of issues with the glow plugs, the first being reported when the truck only had 1,000 miles on it! Every time there is a problem, the dealer just throws glow plugs in it and gives it back. According to the service records, the GP Controller was replaced at one point before I owned the truck. My major concern (aside from it being an inconvenience to keep going back to the dealer) is that my Powertrain Warranty is up in January and what is going to happen when I get stuck footing the bill for this every few months? Is this a known problem with the LML
I have a 2011 LML which I purchased used last year. The truck currently has 55,000 miles on it. Since owning it, I have had 3 separate issues with the glow plugs. I will get a CEL with the Code "Cylinder X Glow Plug Control Circuit" (X representing whatever cylinder it is). I have had issues with the #8 and #7 glow plug and today I got a code for the #6 one. Looking back at the GM Service Records for my truck, it appears as if the previous owner also had a number of issues with the glow plugs, the first being reported when the truck only had 1,000 miles on it! Every time there is a problem, the dealer just throws glow plugs in it and gives it back. According to the service records, the GP Controller was replaced at one point before I owned the truck. My major concern (aside from it being an inconvenience to keep going back to the dealer) is that my Powertrain Warranty is up in January and what is going to happen when I get stuck footing the bill for this every few months? Is this a known problem with the LML motors? Are there any TSBs out there regarding it? Is it worth my time to try and contact GM and above the dealer level and see if they will do anything? Thanks for the info!
My old man has a 2013 one tone. He has owned this truck truck from New! It has 112000km on it now. Every year!!! He has to change out glow plugs. So if you look at glow plugs like a spark plug then after every 3000 to 5000 kms he should be changing his spark plugs/glow plugs??? I feel that is excessive. Gmc should stand behind there defective produce and make a fix. Moving forward i would not recommend this engin/truck to someone. Unless they like changing glow plugs with every oil change.
 

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My old man has a 2013 one tone. He has owned this truck truck from New! It has 112000km on it now. Every year!!! He has to change out glow plugs. So if you look at glow plugs like a spark plug then after every 3000 to 5000 kms he should be changing his spark plugs/glow plugs??? I feel that is excessive. Gmc should stand behind there defective produce and make a fix. Moving forward i would not recommend this engin/truck to someone. Unless they like changing glow plugs with every oil change.
Welcome to DieselPlace
Are the glow plugs being replaced with OEM each time?
Road salts play havoc on electronics. I would give some attention to your grounds and all electrical connections within the harness.
Look for any worn through wire insulation, broken wire, corrosion, etc
 
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It is clear to me that there is definitely something wrong with your truck. Just changing parts has not fixed the problem for a sustained period of time. Yes, having a glow plug go out from time to time is not an unexpected problem, but your repair history tells another completely different story. The problem is going to be getting someone who can accurately diagnose your truck's glow plug system, not just change parts. One thing that kills glow plug systems is batteries with low voltage and extremely cold weather exacerbates that problem. It is particularly important to have your batteries FULLY CHARGED, not just sort-of charged.When the voltage from your battery goes down, the amperage goes up, and then ;you can have a problem. Of course there are various kinds of other circuit problems outlined by OkDually that could be at fault. Electrical problems can be very difficult, if not impossible, to accurately assess unless they are happening during the diagnostic session. Patience is called for.

Back to the basics first. Make sure your batteries are fully charged, have them load tested separately, make sure both ends of the cables are clean and tightly attached. No,you can't tell just by looking at them,. you need to test them. Only takes a common volt meter to do the testing. Go to Youtube and look for 'voltage drop testing' and look for South Main Auto and see what you find there. I think this guy does a very good job and explains things pretty well. And be sure to check your alternator's cables and be sure your charging system is up to snuff. You need everything supplying electricity to work correctly.
 
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My old man has a 2013 one tone. He has owned this truck truck from New! It has 112000km on it now. Every year!!! He has to change out glow plugs. So if you look at glow plugs like a spark plug then after every 3000 to 5000 kms he should be changing his spark plugs/glow plugs??? I feel that is excessive. Gmc should stand behind there defective produce and make a fix. Moving forward i would not recommend this engin/truck to someone. Unless they like changing glow plugs with every oil change.
Does he turn the key to the 'on' position and then wait for the glowplug indicator to go out?

I ran my '11 beyond 112,000 km.
Only ever needed one glowplug.

Not sure if it was related, but it failed / set the on CEL the day after I had started it in a hurry and did not wait.
I did notice that it started fine without waiting -- which is why it registered with me.

FWIW, factory remote start (if it has it) will wait for the glowplugs.

I have followed more than one busy dmax websites since about '08.
Excessive glowplug failures are not a common issue. Something else is going on with that truck.
Perhaps something in the control/monitor circuits for the glowplugs?
 
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