The truck is stuck in four wheel drive and will not disengage. Its one of those that doesn't have the option to put it in or out of four wheel drive, its automatic.
2002 GMC denali truck
Wheel speed sensor(s) The AWD as opposed to 4X4 uses wheel speed sensors to tell if a wheel is not turning at the rpm it should be for speed it's going and will kick it in to AWD with an anomaly in wheel speed
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