Circuit Description

WARNING: This page is about a different car, the 2003 Saturn LW300, 2003 Saturn LW200, 2003 Saturn L300, and 2003 Saturn L200. However, it is still accessible from the selected car via links, so may be relevant.

A normal function of the transmission control module (TCM) is to perform an internal test that verifies the security of the diagnostic and control calibration programming. The programming must contain security codes that enable a software lock to engage. The software lock is designed to prevent unauthorized changes to the diagnostics or control calibrations. The software lock utility is processed independently from the diagnostic and control calibration software and contains application specific data. The software lock data is entered into the TCM during the final assembly of the vehicle.

When the security codes from the diagnostic and shift calibration software fail to engage the software lock, the TCM sets DTC P0602. DTC P0602 is a type A DTC.