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CEL showing all (?) glow plugs bad?
- Thread starter Old_Salty
- Start date
- Staff
- #2
It is hard to believe they would all be bad at once. What is the code you are getting?
Getting the codes for bad glow plugs - P071, P072, P073, etc. - saw all but for cylinder 5. That one may have been there as well. Truck starts well in the cold weather so I am doubtful of the codes displayed. Wondering what would cause all to show bad.
- Staff
- #4
I would check a couple to confirm a bad glow plug. Here is a thread that goes over the removal and testing. http://www.thetruckstop.us/forum/showthread.php?21280-LBZ-Glow-Plug-Replacement
I also found some additional things below to look over if the glow plugs test good.
Condition/Concern:
A vehicle may be brought into the dealer with the SES light on and multiple cylinder glow plug DTCs set. Multiple glow plug DTCs may be caused by internal opens in the glow plugs. There are two different descriptions for an internal open in a glow plug. A fast open glow plug is a plug with an internal open circuitry, but no visual damage to the tip of the plug. A slow open glow plug is a plug that has internal open circuitry, and the tip of the plug is missing or damaged.
Recommendation/Instructions:
Complete the current repair information diagnostics for any symptoms or DTCs found. If the diagnostics for P0671-P0678 led to a glow plug resistance of more than 1 ohm, replace all of the glow plugs. If any of the glow plug tips are missing, the cylinder head must be removed. All debris must be removed from the cylinder. When the tip of a glow plug enters the cylinder, engine damage may occur. Make any engine [FONT=inherit !important][FONT=inherit !important][FONT=inherit ! important]mechanical[/FONT][/FONT][/FONT] repairs as needed.
1. A loose battery feed connection at the starter, alternator, or the Glow Plug Control Module (GPCM) may induce glow plug concerns. When the starter, alternator, or GPCM battery feed circuit has a poor connection, the GPCM will sense a voltage fluctuation, and induce the GPCM to power up the glow plugs. Untimed GPCM cycling may cause glow plug concerns. Inspect the connections at the starter, alternator, and both ends of the battery feed cable to the GPCM. Connector C1 terminal 1 at the GPCM is a quick disconnect type of connector. Make sure terminal fit is clean and tight and the quick disconnect is seated properly. The source or main power feed location differs depending on the vehicle being serviced. On GMT800 C/K model trucks, the power feed stud is located in the Under Hood Bussed Electrical Center (UBEC). To access this power feed stud, the secondary UBEC cover has to be removed. On GMT610 "G" vans inspect the underhood junction block connection. On GMT560 4500/5500 trucks inspect the secondary fuse block connection.
2. There are other electrical scenarios that can induce glow plug concerns. If the glow plug system senses a certain electrical "noise" on the power feed, the glow plugs may also go open. This electrical "noise" may be induced by jump starting, disconnecting the batteries with the ignition in the ON position, or a battery charger being used during a module reprogramming event.
3. If the glowplug DTCs have set on a very low mileage vehicle (below 1000 miles) the glowplugs may have been damaged by the engine start up test conducted at the engine assembly plant.
4. Do not replace the GPCM for all 8 internal opened glow plugs. GPCMs have been returned and inspected with no problem found.
5. Complete all electrical circuit inspections and engine repairs as described above. On 2006 model year vehicles be sure the updated calibration was installed into the GPCM per Campaign 06522. After installing the new GPCM software, complete the Fuel Injector Flow Rate Programming following repair information procedures.
I also found some additional things below to look over if the glow plugs test good.
Condition/Concern:
A vehicle may be brought into the dealer with the SES light on and multiple cylinder glow plug DTCs set. Multiple glow plug DTCs may be caused by internal opens in the glow plugs. There are two different descriptions for an internal open in a glow plug. A fast open glow plug is a plug with an internal open circuitry, but no visual damage to the tip of the plug. A slow open glow plug is a plug that has internal open circuitry, and the tip of the plug is missing or damaged.
Recommendation/Instructions:
Complete the current repair information diagnostics for any symptoms or DTCs found. If the diagnostics for P0671-P0678 led to a glow plug resistance of more than 1 ohm, replace all of the glow plugs. If any of the glow plug tips are missing, the cylinder head must be removed. All debris must be removed from the cylinder. When the tip of a glow plug enters the cylinder, engine damage may occur. Make any engine [FONT=inherit !important][FONT=inherit !important][FONT=inherit ! important]mechanical[/FONT][/FONT][/FONT] repairs as needed.
1. A loose battery feed connection at the starter, alternator, or the Glow Plug Control Module (GPCM) may induce glow plug concerns. When the starter, alternator, or GPCM battery feed circuit has a poor connection, the GPCM will sense a voltage fluctuation, and induce the GPCM to power up the glow plugs. Untimed GPCM cycling may cause glow plug concerns. Inspect the connections at the starter, alternator, and both ends of the battery feed cable to the GPCM. Connector C1 terminal 1 at the GPCM is a quick disconnect type of connector. Make sure terminal fit is clean and tight and the quick disconnect is seated properly. The source or main power feed location differs depending on the vehicle being serviced. On GMT800 C/K model trucks, the power feed stud is located in the Under Hood Bussed Electrical Center (UBEC). To access this power feed stud, the secondary UBEC cover has to be removed. On GMT610 "G" vans inspect the underhood junction block connection. On GMT560 4500/5500 trucks inspect the secondary fuse block connection.
2. There are other electrical scenarios that can induce glow plug concerns. If the glow plug system senses a certain electrical "noise" on the power feed, the glow plugs may also go open. This electrical "noise" may be induced by jump starting, disconnecting the batteries with the ignition in the ON position, or a battery charger being used during a module reprogramming event.
3. If the glowplug DTCs have set on a very low mileage vehicle (below 1000 miles) the glowplugs may have been damaged by the engine start up test conducted at the engine assembly plant.
4. Do not replace the GPCM for all 8 internal opened glow plugs. GPCMs have been returned and inspected with no problem found.
5. Complete all electrical circuit inspections and engine repairs as described above. On 2006 model year vehicles be sure the updated calibration was installed into the GPCM per Campaign 06522. After installing the new GPCM software, complete the Fuel Injector Flow Rate Programming following repair information procedures.
- Staff
- #5
I'd be willing to bet it is a wiring or more likely a module issue instead of all the plugs. Just call me captain obvious...:agreed:
Last edited:
- Staff
- #6
Check the 175 amp fuse that goes to the glow plug controller. Sounds like it got shorted out and popped as that is about all I can think of that would cause it say all of them are bad at once.
- Staff
- #7
That stuff don't happen with a dino-diesel... 
Just sayin' :hihi:
Just sayin' :hihi:
- Staff
- #8
Yeah, but it must get pretty tiring having to tape 8 new 'D' cell batteries in place every week in the cold weather.That stuff don't happen with a dino-diesel...
Just sayin' :hihi:
Snot Rocket
New Member
I'm still new here and learning. But wouldn't the first thing to do is check to see if the glow plugs are bad?
Can you do the simple test light test to see if there bad on the LLY/LBZ?
Can you do the simple test light test to see if there bad on the LLY/LBZ?
Last edited by a moderator:
- Staff
- #10
Yes and no. LBZ glow plugs are nothing like the glow plugs used in older diesels. You can still check them for resistance though, but don't daree hook em to a battery to see if they glow as they are 4.7V and require a pulse width modulated signal to power them. And the newer trucks rarely if ever lose all the glow plugs at the same time, normally only one or two at a time go out.
More confused now. I cleared the codes when I read them. CEL went off. 20 degrees F here this morning and the glow plugs functioned fine and no CEL after start. Appreciate the CEL being off, but what caused it in the first place? Don't recall jump starting anything or any other issue when the CEL came on... It's quickly becoming a moot point as I may be pulling the trigger on a 2012. artay:
artay: