This information applies to 2006 Chevrolet Express, Kodiak, Silverado, GMC Savanna, Sierra, and TopKick
equipped with the 6.6L (RPO - LBZ or LLY) Duramax Diesel Engine.
A vehicle may have 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 has an internal open circuitry, but no visual damage to the tip of the plug.
A slow open glow plug has internal open circuitry, and the tip of the plug is missing or damaged.
Complete the SI diagnostics for any symptoms or DTCs found. If the diagnostics for P0671 - P0678 lead to a glow plug resistance of more than 1 ohm, replace all of the glow plugs. If any glow plug tip is missing, remove the cylinder head and remove all debris from the cylinder. When the tip of the glow plug enters the cylinder, engine damage may occur. Make any engine mechanical 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, generator, or GPCM battery feed circuit has a poor connection, the GPCM senses a voltage fluctuation, and induces the GPCM to power up the glow plugs. Untimed GPCM cycling may cause glow plug concerns.
Inspect the connections at the starter, generator, and both ends of the battery feed cable to the GPCM. Connector C1 terminal 1 at the GPCM is a quick disconnect connector. Make sure the 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 C/K trucks, the power feed stud is located in the Under Hood Bussed Electrical Center (UBEC). To access this power feed stud, remove the secondary UBEC cover.
- On G vans, inspect the underhood junction block connection.
- On 4500/5500 trucks, inspect the secondary fuse block connection.
2. Other electrical scenarios can induce glow plug concerns. If the glow plug system senses a certain electrical noise on the power feed, the glow plugs may 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 glow plug DTCs have set on a very low mileage vehicle (below 1000 miles), the glow plugs may have been damaged by the 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. After necessary repairs are completed, update the calibration in the GPCM. See campaign 06522. Install the new GPCM software and complete Fuel Injector Flow Rate Programming following SI procedures.
TIP:Â Add-on remote starter kits or alarm kits must be removed before any glow plugs are replaced. Interruptions to normal starting procedures may induce glow plug concerns.
- Thanks to Don Langer
equipped with the 6.6L (RPO - LBZ or LLY) Duramax Diesel Engine.
A vehicle may have 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 has an internal open circuitry, but no visual damage to the tip of the plug.
A slow open glow plug has internal open circuitry, and the tip of the plug is missing or damaged.
Complete the SI diagnostics for any symptoms or DTCs found. If the diagnostics for P0671 - P0678 lead to a glow plug resistance of more than 1 ohm, replace all of the glow plugs. If any glow plug tip is missing, remove the cylinder head and remove all debris from the cylinder. When the tip of the glow plug enters the cylinder, engine damage may occur. Make any engine mechanical 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, generator, or GPCM battery feed circuit has a poor connection, the GPCM senses a voltage fluctuation, and induces the GPCM to power up the glow plugs. Untimed GPCM cycling may cause glow plug concerns.
Inspect the connections at the starter, generator, and both ends of the battery feed cable to the GPCM. Connector C1 terminal 1 at the GPCM is a quick disconnect connector. Make sure the 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 C/K trucks, the power feed stud is located in the Under Hood Bussed Electrical Center (UBEC). To access this power feed stud, remove the secondary UBEC cover.
- On G vans, inspect the underhood junction block connection.
- On 4500/5500 trucks, inspect the secondary fuse block connection.
2. Other electrical scenarios can induce glow plug concerns. If the glow plug system senses a certain electrical noise on the power feed, the glow plugs may 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 glow plug DTCs have set on a very low mileage vehicle (below 1000 miles), the glow plugs may have been damaged by the 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. After necessary repairs are completed, update the calibration in the GPCM. See campaign 06522. Install the new GPCM software and complete Fuel Injector Flow Rate Programming following SI procedures.
TIP:Â Add-on remote starter kits or alarm kits must be removed before any glow plugs are replaced. Interruptions to normal starting procedures may induce glow plug concerns.
- Thanks to Don Langer
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