Before checking the fluid level in a manual transmission, what must a technician do?

The correct approach before checking the fluid level in a manual transmission involves consulting the service information for the specified procedure. This step is crucial because different vehicle models may have unique requirements for checking the fluid level, including the recommended types of fluid, the location of the fill and drain plugs, and the specific temperature conditions under which the check should be performed.

Understanding the service manual ensures that the technician follows the correct protocol, which can prevent damage to the transmission and ensure accurate fluid level readings. Each manufacturer may have specific instructions that differ, such as whether the vehicle needs to be on a level surface or if it should be at operating temperature, making it imperative to refer to the appropriate documentation beforehand.

The other choices do not address this foundational step and may lead to improper procedures. For instance, draining all existing fluid is neither necessary nor advisable before just checking the level. Filling the transmission prematurely does not verify whether the current level is adequate or if there are leaks present. Also, using a vacuum pump to extract fluid is not a standard procedure for checking fluid levels and could potentially result in fluid loss or contamination without assessing the current condition first. Hence, verifying the proper procedures through service information is essential for effective maintenance.