02 yukon denali security light stays on will not

Several GM products, including the Chevrolet Impala and Malibu, the Oldsmobile Alero, the Pontiac Grand Prix, and Saturn Ion, have issues with the Security light coming on. This is many times an indication of a failing Body Control Module (BCM). Initially, the Security light will come on then go off, progressing to a constant on light, before the car will refuse to start. Other symptoms may include erratic action of electronics, a clicking sound coming from the glove box, and the air conditioning failing to blow cold air. I recommend a shop that specializes in the electronic systems of vehicles to diagnosis and make the necessary repairs. They should keep the car until they replicate the symptoms described. A new BCM from GM should cost about $230; plan on another $200 for them to diagnose the problem, replace the unit, and program the new unit. The dealers quote between $700 and $1,100 for the same repair. My experience and the experiences I have read on the internet, indicate the new BCM should last only about a year.

The security system (VATS/PassKey) is having problems, it's typical on those trucks. You can find a great write-up here: http://newrockies.ca , it was the only thing that saved my Park Avenue.