| Subject: | New Diagnostic Procedure for DTC P2900 Available for 7.8L Engine | 
| Models: | 2004*-2006 Chevrolet C6500-C8500 and T6500-T8500 Series Medium Duty | 
 | 2004*-2006 GMC C6500-C8500 and T6500-T8500 Series Medium Duty | 
 | 2004*-2006 Isuzu FTR/FVR/FXR/HTR/HVR/HXR Medium Duty Commercial Models | 
 | *(2004 models with RPO CTF only) | 
 
This bulletin is being revised to include the 2004 (with RPO CTF) models. Please discard Corporate Bulletin Number 06-06-04-014 (Section 06 -- Engine/Propulsion System).
This bulletin is being issued to inform dealers that a new diagnostic procedure for DTC P2900 - Turbocharger Vane Position Stuck has been added to the Service Information (SI) for the above-listed vehicles.
Detailed information can be found in SI under Engine/Engine Controls - 7.8L / Diagnostic Information and Procedures / DTC P2900. Reference SI Document ID# 1453023.
This diagnostic procedure can be performed using the Tech 2® by building the vehicle as a 2006 MY.
|     •  | Select Special Functions. | 
 
|     •  | Select Engine Output Controls. | 
 
Important: 
|    •  | If this new procedure does not work, you must call GMICT Technical Assistance at 1-800-633-4863 for further instructions. Canadian French dealers should call the GM Canada Technical Assistance Centre (TAC). | 
 
|    •  | You must meet all the required conditions as noted in the Service Information before performing this diagnostic procedure. |