2012 GMC Sierra Owner's Manual - Page 400

10-14 Vehicle Care Change the fluid and filter at the scheduled maintenance intervals listed in Maintenance Schedule on page 11‑3. Be sure to use the transmission fluid listed in Recommended Fluids and Lubricants on page 11‑12. Before checking the fluid level, prepare the vehicle as follows: 1. Start the engine and park the vehicle on a level surface. Keep the engine running. 2. Apply the parking brake and place the shift lever in P (Park). 3. With your foot on the brake pedal, move the shift lever through each gear range, pausing for about three seconds in each range. Then, move the shift lever back to P (Park). 4. Allow the engine to idle (500 - 800 rpm) for at least 1 minute. Slowly release the brake pedal. 5. Keep the engine running and press the Trip/Fuel button or trip odometer reset stem until TRANS TEMP (Transmission Temperature) displays on the Driver Information Center (DIC). Automatic Transmission Fluid (6-Speed Transmission) When to Check and Change Automatic Transmission Fluid It is usually not necessary to check the transmission fluid level. The only reason for fluid loss is a transmission leak or overheated transmission. If a small leak is suspected, then use the following checking procedures to check the fluid level. However, if there is a large leak, then it may be necessary to have the vehicle towed to a dealer service department and have it repaired before driving the vehicle further. Notice: Use of the incorrect automatic transmission fluid may damage the vehicle, and the damages may not be covered by the vehicle warranty. Always use the automatic transmission fluid listed in Recommended Fluids and Lubricants on page 11‑12. How to Check Automatic Transmission Fluid Notice: Too much or too little fluid can damage the transmission. Too much can mean that some of the fluid could come out and fall on hot engine parts or exhaust system parts, starting a fire. Too little fluid could cause the transmission to overheat. Be sure to get an accurate reading if checking the transmission fluid.