Can I control the volume of my AirPods 4 with the force sensor on the stem?

There is no volume control on the AirPods 4.

Use controls and gestures with your AirPods - Apple Support

AirPods 4 and AirPods 4 (ANC) controls and gestures

With the force sensor on the stem of AirPods 4 (both models), you can do any of the following:

• Play and pause audio: Press the stem. To resume playback, press it again.
• Play the next track: Double-press the stem.
• Play the previous track: Triple-press the stem.
• Answer a call: When you receive a call, press the stem.
• Switch between Noise Cancellation, Transparency, and Adaptive Audio noise control modes: On AirPods 4 (ANC) only, you can set either of your AirPods to perform this action when you press and hold the stem. See Change what the force sensor or Touch control does.
• Activate Siri: You can set either of your AirPods to perform this action when you press and hold the stem. See Use Siri with AirPods.

Use head gestures to respond to Siri

• Accept a call or reply to notifications and messages: Nod your head up and down.
• Decline a call or dismiss notifications and messages: Shake your head side to side.

Note: To use head gestures to respond to Siri, Announce Calls and Announce Notifications must be on. See Use Siri to announce calls or notifications.