DTC P0606: Control Module Internal Performance: Description
WARNING: This page is about a different car, the 2001 Cadillac Seville, 2001 Cadillac Eldorado, and 2001 Cadillac DeVille. However, it is still accessible from the selected car via links, so may be relevant.
Powertrain Control Module (PCM) is capable of diagnosing a malfunction within the controller. If PCM detects a malfunction within the controller, DTC P0606 will set.