P0106 Diagnostic Code in 2004 Chevrolet Trailblazer - Map Sensor Voltage Issue

I'm experiencing a P0106 diagnostic code on my 2004 Chevrolet Trailblazer. The Manifold Absolute Pressure (MAP) sensor is showing inconsistent readings: I've checked the voltage and am getting 5 volts for power, proper ground, and reference voltage. When the key is ON, the signal reads 4.55 volts; when the engine is running, it drops to 1.10 volts and fluctuates under load (during acceleration). No vacuum leaks have been detected. The sensor appears to be functioning but the readings are unstable. What could be causing this? Any suggestions or troubleshooting steps would be greatly appreciated. Thanks!