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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have a 2007 Chey Silverado 2500 4X4 6.6L TD Crew Cab. Over

Customer Question

I have a 2007 Chey Silverado 2500 4X4 6.6L TD Crew Cab. Over the last six months I have had error codes for glow plugs 7 and 8. I have had the following replaced:
All 8 glow plugs replaced last August. 3 day later error codes for glow plugs 7 and 8 return.
Replaced glow plugs 7 and 8 again. 1 day later error codes for glow plugs 7 and 8 return.
Replaced fuses in glow plug harness. 1 day later error codes for glow plugs 7 and 8 return.
Replaced Glow Plug Control Module. 1 day later error codes for glow plugs 7 and 8 return and temperature now reading 30 DEG over at 208 DEG.
Replaced both thermostats coolant and temperature sensor. 1 day later error codes for glow plugs 7 and 8 return and temperature still reading 30 DEG over at 208 DEG.
What could be the issue.... Alternator, ECM????
Submitted: 9 months ago.
Category: Chevy
Expert:  Juan Crespo replied 9 months ago.

The OBD-II computer takes a snap shot of the most relevant engine parameters at the same it sets a particular code. Knowing that, I need to ask you some questions in order to get an idea of how to best help you solve this issue:

  • What compelled replacement of all those parts you mention?
  • What are the specific codes we're talking about?
  • Was any of the accompanying freeze frame data saved? If so, can you upload it along with its corresponding code?
Customer: replied 9 months ago.
Original problem was glow plug 7 and 8 badI don't know the codes. Ivan stop by the prolegs on the way home and get the current codes.No
No
Expert:  Juan Crespo replied 9 months ago.

I'm sorry, but it looks like I won't be able to help you. I'll opt out so others may try. Please do not reply until another expert responds or the site will revert the request back to me.

Best Regards.

Expert:  piciu1982 replied 9 months ago.

hi, can you provide me your VIN nr

Customer: replied 9 months ago.
Hello,
Im at work and will provide the vin when I get home.Thanks
Customer: replied 9 months ago.
1gchk23dx7f180232
Expert:  piciu1982 replied 9 months ago.

you have to check wiring between glow plug control module and glow plugs, sometimes terminal by the glow plug is rusted and needs to be replaced, easiest way to check it is disconnect GPCMand use a test light connected to battery positive terminal and touch all terminals in the plug, if glow plug is good, test light will illuminate, it has to be regular test light !!, test light will illuminate on 9 terminals 8 glowplugs and gpcm ground !

Customer: replied 9 months ago.
Roger, I will test it this weekend and let you know what I find. Now would this affect the temperature reading? It just started reading 30 degrees over here in January. I have also lost 3 mile to a gallon as well. Last time GM checked the system the only issue they could find was the temperature sensor reading off. They said that is was causing the computer to send the wrong voltage to the glow plugs causing the gpc to give an error code. This is why I replaced the coolent, thermostats and temperature sensors. Before this it never read over 181 even on very hot days
Expert:  piciu1982 replied 9 months ago.

best way to check temperature reading is with the scan tool after it sits overnight, all temperatures should b very close or even . so intake air, coolant temp, egr, egt sensors, transmission oil, engine oil, you will know right away if sensor is bad or with one is causing problems , also as for glow plugs it will delay glow plugs but will never set circuitd codes for individual glow plugs