1997 GMC Sonoma Owner's Manual - Page 257

Then, without shuttingoff the engine, follow these steps: 3. Check both sides of the dipstick, and read the lower level. The fluid level must be in the COLD area for a cold check or in the HOT area or cross-hatched area for a hot check. 1. Flip the handle up and then pull out the dipstick and wipe it with a clean rag or paper towel. 2. Push it back in all the way, wait three seconds and then pull it back out again. 4. If the fluid level is in the acceptable range, push the dipstick back in all the way; then flip the handle down to lock the dipstick in place.