See Figure 1
Some audio systems have an anti-theft system built into them. The system requires the operator to select and program a 3-digit code into the unit. If no code is installed, the anti-theft system is inoperative; the audio unit functions as a normal unit, even after power is restored after disconnection. Complete instructions for installing the code are found in the owners manual for the vehicle. As long as power remains connected to the unit, it may be used in the normal fashion. Once power is disconnected from the unit, the audio unit will not function until the correct code is re-entered. This will render the unit useless if stolen; there is no way to retrieve the stored code.
The anti-theft code may be canceled or changed following an exact procedure explained in the vehicles owners manual. If an error is made during the procedure, the designation ERR appears in the digital window. Once 10 errors have occurred, the word HELP appears and the system will not work regardless of codes or power. If the HELP message appears, the unit must be taken to a Toyota dealer to be reset.
All of the units equipped with this system have the words ANTI THEFT SYSTEM visible on the front of the unit, usually on the tape player door. Care must be taken when working on these vehicles anytime the battery cable must be disconnected or if fuses are removed during other test procedures. If its your vehicle, chances are good that you know the code (if one was installed); if its a friends vehicle, you could be in trouble. Always check with the owner before beginning any work which could interrupt power to the audio unit. For any further information on your particular unit, see your owners manual.