Cellular Signal Strength Meter over Car Handsfree Systems

I'm noticing some strange behavior with my 4S and my car's handsfree system (2007 Acura RDX Handsfreelink). The signal strength meter in the handsfreelink display seems to get 'stuck' shortly after I lock my phone. For example, if it gets stuck at one bar and I don't make any calls, I can drive around all day and it will always say one bar. However, if I drive into a higher strength area, then pick up my 4S and press the home button, I can watch the signal strength meter on the phone immediately start climbing up. The handsfreelink display then reflects that.

Has anyone else noticed this behavior? It's kind of annoying because I can no longer just hit the car handsfreelink button to check my strength before making a call.

I have some theories, but I'd like to rule out a bum 4S first. Of others see it, then I can rule that out. I'm wondering if it is a change they've made with iOS5, or if it is related to the 4S and/or Bluetooth 4.0. Since Bluetooth 4.0 is supposed to be consume less power, I'm wondering if signal strength meter updates get suspended after a period of phone inactivity. Alternatively, I'm wondering if it is something Apple did to squeeze more power out of the 4S battery - ie: shut down signal strength meter updates when the screen is off. As I said, I do see the signal strength meter on the phone gradually rise (takes 2-3sec) to the new level after I hit the home button. It seems to start out at the 'stuck' point.

Does anyone have any thoughts?