Where is the Body Control Module on 2002 Saturn L300?

Answer 1

Supposedly above the glovebox, but not exactly sure. Planning on replacing mine, too, but heard you must reprogram it from the old BCM to retain your original mileage and the VIN. Otherwise, there is a manual cycle program to train the new BCM to work with the PCM so you can start the car. See procedure below:

Here's the immediate problem you need to know and understand about BCM's; being a separate computer to handle more electronics that the engine computer doesn't need to handle (the PCM), the BCM handles OBD II duties and controls the vehicle Passlock anti-theft system among other chores. The anti-theft system requires the BCM to communicate with a security signal that's detected at the ignition switch during rotation when turning ON the ignition. If the security signal isn't recognized by the BCM the BCM automatically sends signals to the PCM that kills the engine from running by disabling the fuel pump and injectors. This is the heart and soul of GM's vehicle anti-theft system - no fuel pump means no fuel and pressure to the injectors as well as disabling injector pulses. A dead engine. You can crank the engine all day but while the security light flashes during starting the engine will never fire up; no fuel pressure to supply dead injectors. The BCM sends a password to the PCM disabling part of it from operating. If the BCM doesn't have the security code to recognize the ignition switch signals the BCM won't work at all. However, any PCM, BCM, or ignition switch assembly that's replaced requires what's described as a Passlock re-learn procedure to synchronize the three subassemblies for proper operation. This either takes place at Saturn or during a 30-minute DIY procedure in three 10-minute cycles. The procedure is basically to leave the ignition ON for 10-minutes, cycling the ignition OFF and then ON for another 10-minutes and once more until repeated three times, never starting at any time. After the third cycle the ignition can be turned to start the engine to confirm that all components have successfully been synchronized. A failure to start means an incorrect re-learn procedure was done and needs to be repeated all over again. The security light will flash during the process and eventually turn off altogether as indication of successful re-learing security codes for any new part replaced. What isn't changed are the VIN and mileage that Saturn equipment can do. The security system is divided into three parts; the ignition switch sensors, the PCM, and the BCM. Any one of these subassemblies being replaced requires the BCM to relearn the new replacement part otherwise you'll just have a dead engine unable to run. New BCM's come as blanks that Saturn address' with their Techtool II with VIN and mileage copied from the failed BCM. 'Field' BCM's removed from vehicles still retain VIN and mileage that can only be changed by Saturn. There may be other programmed accessories that have to considered to be compatible to the original one removed for replacement.