There is a software problem in the engine
control computer that causes this. You will need to have your dealer reprogram the computer with the updated software. See bulletin below describing this conditon and the fix.
Bulletin No.: 08-08-49-001
Date: February 05, 2008
Inaccurate Fuel Gage Readings, Fuel Gage Reads Empty when There is Fuel in Tank, Fuel Level Low Message in DIC, DTC P2066 Set (Reprogram ECM) Models:
2004-2006 Cadillac SRX
2004-2007 Cadillac CTS
2005-2007 Cadillac STS
with 2.8L or 3.6L Engine (VINS T, 7 - RPOs LP1, LY7)
Some customers may comment that the fuel gage reads empty when there is fuel in the tank. Also, the driver information center may display the "Fuel Level Low" message.
A scan tool may reveal DTC P2066 set in the ECM.
An issue with the ECM software has been identified that will cause the ECM to increment the fuel used incorrectly if the vehicle is driven for a number of short trips with frequent key cycles between refueling events.
If routine diagnosis using SI does not reveal any obvious cause, then reprogram the ECM with updated calibration files using the TIS2WEB Service Programming System (SPS) application.