We are in the coldest time of year in most places where the glow plugs are usually needed to aid in start up. It is also when glow plug system failures start showing their face. Most of the time it is a simple glow plug replacement which can be diagnosed fairly quickly with something as simple as a test light. If the glow plug control module ends up needing to be replaced on 2006+ LBZ and newer engines, the glow plug control module does require programming. The earlier 2001-2005 LB7/LLY engines, the glow plug control modules are plug and play with no programming required. The LBZ and newer engines will need the injector flow rates programmed into the glow plug control modules. The programming will require use of a GM Tech 2 scan tool or equivalent. This also applies if you are replacing injectors or an engine control module on 2006 and newer Duramaxs.

Fuel Injector Flow Rate Programming

Circuit/System Description

The control functions for the fuel injection system are integrated in the engine control module (ECM). Each injector's flow rate information and cylinder position are stored in the memory of both the glow plug control module (GPCM) and the ECM.
The fuel injector flow rate programming must be done when any of the following procedures are performed:

• The ECM is replaced
• The GPCM is replaced
• Any fuel injectors are replaced

If the ECM does not communicate, the flow rate information can be retrieved from the GPCM. If both control modules fail to communicate, the fuel injector flow rate information, or injection quantity adjustment (IQA) flow rate numbers, will need to be retrieved from each individual injector.

Before Programming A Control Module

Important: DO NOT program a control module unless you are directed by a service procedure or you are directed by a General Motors Corporation service bulletin. Programming a control module at any other time will not permanently correct a customers concern.

Ensure the following conditions are met before programming a control module:

• Vehicle system voltage
• There is no charging system concern. All charging system concerns must be repaired before programming a control module.
• Battery voltage is between 12-16 volts. The battery must be charged before programming the control module if the battery voltage is low.
• A battery charger is NOT connected to the vehicle battery. Incorrect system voltage or voltage fluctuations from a battery charger may cause programming failure or control module damage.
• Turn OFF or disable any of the following systems that may put a load on the vehicle battery:
• Twilight sentinel
• Interior lights
• Daytime running lights (DRL)-Applying the parking brake, on most vehicles, disables the DRL system. Refer to the Owner's Manual.
• HVAC systems
• Engine cooling fans, etc.
• The ignition switch is in the proper position-The scan tool prompts you to turn ON the ignition, with the engine OFF. DO NOT change the position of the ignition switch during the programming procedure, unless instructed to do so.
• All of the following tool connections are secure:
• The connection at the data link connector (DLC)
• The voltage supply circuits
• DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.

Circuit/System Verification

Review the Display ECM & GPCM Inj. Flow Rates parameter with a scan tool. All cylinders should be programmed with a flow rate number. Both the GPCM and the ECM should be programmed with the same flow rate numbers for the corresponding cylinders.

Circuit/System Testing

Important: If the flow rate number is not available in either control module, the numbers will need to be retrieved from each individual injector.

Fuel Injector Identification Numbers

• With a scan tool installed, enter the vehicle information and select the following options:
• Engine Control Module
• Module Setup
• Injector Flow Rate Programming
• Display ECM & GPCM Inj. Flow Rates

 

• Record all flow rate numbers with the corresponding cylinders from the control modules.

Important: When installing a new fuel injector, ensure that the IQA data number from the yellow IQA Data Tag, shipped with the new injector, is programmed to the correct cylinder

• If any injectors are replaced, go to Reprogram Injector Flow Rates parameter and enter the flow rate number of the new injector to the corresponding cylinder. The flow rate numbers will automatically update both control modules.
• If the ECM was replaced, go to Copy GPCM Inj. Flow Rates to ECM parameter and reprogram the ECM. This will update the ECM with the GPCM flow rate numbers.
• If the GPCM was replaced or the flow rate numbers are not the same for both modules, go to Copy ECM Inj. Flow Rates to GPCM parameter and reprogram the GPCM. This will update the GPCM with the ECM flow rate numbers.

If both control modules were replaced, go to Reprogram Injector Flow Rates parameter and enter the previously recorded flow rate numbers or the numbers retrieved from each individual injector, to the corresponding cylinders