1998 GMC Sonoma Owner's Manual - Page 367

Ignition Transmission Lock Check While parked,and with the parking brake set, try to turn the ignition key to LOCK in each shift lever position. 0 Park on a fairly steep hill, with the vehicle facing downhill. Keeping your foot on the regular brake, set the parking brake. 0 With an automatic transmission, thekey 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 theshift lever is in REVERSE (R). To check theparking brake's holding ability: With the engine runningand transmission in NEUTRAL (N), slowly remove foot pressure from the regularbrake pedal. Do this untilthe vehicle is held by the parking brake only. To check the PARK (P) mechanism's holding ability: With the engine running, shift to PARK (P). Then release all brakes. On vehicles with a key release button, to turn the key try to LOCK without pressing the button. The key should turn to LOCK only when you press the key button. only in LOCK. On all vehicles,the key should come out 0 Underbody Flushing Service At least every spring, use plain water to flush any corrosive materials from the underbody. Take care to clean thoroughly any areas where mud and other debris can collect. Parking Brake and Automatic Transmission PARK (P) Mechanism Check 1 When you are doing this check, your vehicle could beginto move. You or others could be injured and property could be damaged. Make sure thereis room in frontof your vehicle in case it begins to roll. Be ready to apply the regular brake at once should the vehicle beginto move. 7-45