by Dave Martin
With the ever-increasing cost of Radio-Tape-CD players, it is no surprise that the theft of these systems has also increased.
General Motors has responded to this problem by installing anti-theft systems into many of their entertainment centers. Delco Lock was first introduced in 1986 by Pontiac and used until 1989. This basic system works in conjunction with radio controls located on the steering wheel. If memory power is removed from the radio, "LOC" will appear on the digital display when power is restored.
Unlocking the radio is a basic two-step procedure. First, turn the ignition and radio on, then depress the "mute" button on the steering wheel control pad for about 10 seconds. This will send a digital signal to the radio, restoring it to normal operation. If the control pad does not work, there are two other ways to unlock it. The radio may be sent in to an authorized repair center to be unlocked and will be programmed to "wake up" one time only in an unlocked mode. The other method requires using a bi-directional scan tool which has the capability to communicate through a radio data line at the ALDL connector. If you will be removing power from a vehicle with this system, try the radio control pad first. If it doesn't work, notify the customer and explain the two options.
In 1988, another version of Delco Lock was introduced and was used until 1995 by Pontiac, Oldsmobile, and Buick. Again, this version is only found on vehicles with radio steering wheel controls. If memory power is removed from the radio, it will be locked when power is restored. The difference is that after power is restored, the radio will automatically communicate with the steering wheel control module and unlock itself. If a new steering wheel control pad is installed, turn the ignition and radio on. Depress the station preset buttons in positions 1 and 4 to unlock the radio and return it to normal operation.
Delco Lock II (also called Theftlock), the next generation of anti-theft controls, features an owner-programmed lock code which is entered through the radio controls. If the customer programs a lock code into the radio and memory power is lost, "LOC" will appear after power is restored. The locking code must be entered to allow its use. If the customer does not have the code number, the radio may be unlocked by an authorized General Motors facility using special access codes.
Since there are numerous radio systems available, it is important to obtain the RPO codes from the decal on the vehicle. Radio codes start with the letter "U." Compare these codes with your repair manual to match the systems and service procedures. If you have any questions, give me a call.
found this online, hope that it helps
No Longer in the Stable-1992 SSEi-- RIP