1995 GMC Yukon Owner's Manual - Page 462

Brake-Transmission Shift Interlock -- BTSI I I A CAUTION: I When you are doing this check, the vehicle could move suddenly. If it does, you os others could be injured. Follow the steps below. I 1 . Before you start, be sure you have enough room around the vehicle. It should be parked on a level surface. 2. Firmly apply both the parking brake (see "Parking Brake" in the Index if necessary). NOTE: Be ready to apply the regular brake immediately if the vehicle begins to move. 3. With the engine off, turn the key to the RUN position, but don't start the engine. Without applying the regular brake, try to move the shift lever out of PARK (P) with normal effort. I f the shift lever moves out of PARK (P), your vehicle's BTSI needs service. Steering Column Lock While parked, and with the parking brake set, try to turn the key to LOCK in each shift lever position. 0 With an automatic transmission, the key should turn to LOCK only when the shift lever is in PARK (P). With a manual transmission, the key should turn to LOCK only when the shift lever is in REVERSE (R). 0 On vehicles with a key release button, try to turn the key to LOCK without pressing the button. The key should turn to LOCK only with the key button depressed. On vehicles with a key release lever, try to turn the key to LOCK without pressing the lever. The key should turn to LOCK only with the key lever depressed. On all vehicles, the key should come out only in LOCK. 7-94