Emissions Recall - General Motors has decided to conduct a Voluntary Emission Recall involving certain vehicles. The vehicle?s Engine Control Module (ECM) may have been reprogrammed during service with incorrect diagnostic software. If that occurred, the ECM may not accurately diagnose a fault in the auxiliary fuel tank system or the four wheel drive system. Further, the ECM may incorrectly report a fault or illuminate the malfunction indicator lamp (check engine light) on vehicles not equipped with these two systems. Dealers are to reprogram the ECM.