You should NOT attempt to check the transmission fluid level yourself without the proper scan tool. Incorrectly attempting to check or add fluid can damage the transmission.
Here's what you should do:
1. Take it to a qualified mechanic: This is the safest and most reliable method. They have the diagnostic equipment and expertise to properly assess the transmission fluid condition and level.
2. Find a shop with a compatible scan tool: If you insist on checking yourself (strongly discouraged), you need a professional-grade scan tool capable of communicating with the 2005 Cadillac STS's TCM and displaying transmission fluid temperature and level data. Generic OBDII scanners usually won't suffice for this. Many independent repair shops may offer this service for a fee even if you don't have them completely service the transmission.
Why no dipstick?
Modern automatic transmissions, particularly those in luxury vehicles like the 2005 Cadillac STS, often use a sealed system without a dipstick. This is primarily due to the complexity of the transmission and the need for precise fluid levels under various operating temperatures. A dipstick wouldn't provide an accurate reading.
In short, leave this to the professionals. Improperly handling transmission fluid can lead to costly repairs.
