2009 Chevrolet Silverado 2500 HD Extended Cab Owner's Manual - Page 435

How to Check Automatic Transmission Fluid Notice: Too much or too little fluid can damage your 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 you check your transmission fluid. 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 one 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). 6. Using the TRANS TEMP reading, determine and perform the appropriate check procedure. If the TRANS TEMP reading is not within the required temperature ranges, allow the vehicle to cool, or operate the vehicle until the appropriate transmission fluid temperature is reached. 5-25