i have an 05 silverado crew. 5.3 Z71 4wd with 175k miles. i drive it every day on average of about 1000 miles a week. around a year ago i had the service brake system and abs light come on while driving down the interstate 75-85 mph. it would come on every now and then only at higher speed and then turn off minutes later or untill i slowed down. this is on and off for a year now. last month at 50mph my service engine soon light turns on, brake system light turns on, and airbag light turned on all in a row at one time. advance auto says engine light is oxygen sensor- front right. air bag light is rarely on and off, but brake system msg comes on all the time 70-80 mph. this weekend i went out of town, brake light comes on again and speedometer goes crazy, fastly fluctuating-showing between 65-80 up and down, up and down, although maintaining a speed of around 75. it lasts a few seconds or untill i reduce speed to about 70 and it will be back to normal. im thinking speed sensor on the speedo, but what about the brake msg, and that ghostly airbag light????? please help!!!!

the vss output goes to the pcm first so if your trans isnt freaking out its something in or the ground for the cluster. and given the millions of complaints ive read about the cluster and the work trucks we have at work hav ehad to have the cluster replaced i would suspect that. as far as your abs and service air bag you can go to a dealer or a mechanic that has the higher end scanners and see if there are body codes stored and go from there. the o2 needs to be more specific, there are a ton of codes refering to the o2 and only a few would suggest it needs to be replaced, there are circuit codes heater codes, rich or lean codes etc...