there is a bulletin for reprogramming these.
#05-06-04-012A: Service Engine Soon (SES) Light On, Fuel Gauge Reads Empty with Fuel in Tank, Fuel Transfer System Disabled, DTCs Set for LB7 or LLY, (Reprogram Engine Control Module with New Fuel System Calibration) - (Aug 22, 2006)
Subject:Service Engine Soon (SES) Light On, Fuel Gauge Reads Empty with Fuel in Tank, Fuel Transfer System Disabled, DTCs P0461, P0462, P0463, P1172, P1431, P1432, P1433 for LB7 and P0461, P0462, P0463, P2066, P2067, P2068, P2636 for LLY Set (Reprogram Engine Control Module with New Fuel System Calibration)
Models:2003–2005 Chevrolet Kodiak C4500–C5500 Series
2003–2005 GMC Topkick C4500–C5500 Series
with 6.6L Diesel Engine (VINs 1, 2 — RPOs LB7, LLY)
and Dual Fuel Tanks (RPO NG6)
This bulletin is being revised to update/add information. Please discard Corporate Bulletin Number 05-06-04-012 (Section 06 — Engine/Propulsion System).
Some customers may comment that the fuel gauge reads empty when there is actually fuel in the tank(s). Diagnosis may indicate that one of the following DTCs has set.
DTC (RPO LB7)
DTC (RPO LLY)
If the vehicle has Fuel System Calibration Part Number 93803804, 93803921 or 93441652 installed, and the rear fuel tank is filled beyond the point where the automatic shut-off feature in the fuel station pump handle has cancelled, it takes longer than expected for the fuel level to drop to the point where the sender indicates fuel has transferred. The condition may cause one or more of the above DTCs to set.
If the vehicle has Fuel System Calibration Part Number 93803804, 93803921 or 93441652 installed, reprogram the ECM with the latest fuel system calibration before diagnosing the fuel system. The new fuel system calibration has been released to prevent any DTCs from setting due to higher than expected fuel level.
This calibration, or any that follow, is designed to address this concern. Refer to Service Programming System (SPS) using the appropriate Service Information (SI) procedures. The new calibrations were available to dealerships as part of TIS2000 incremental satellite update version 6.5 for 2006, which was broadcast to dealers on 06/11/2006. For the dealerships that use CDs, the CD version is 7.0 for 2006, which was mailed to 07/05/2006. As always, make sure your Tech 2® is updated with the latest software version.