Audi A4 B8 2.0TDI Faulty P2564 Code with Flashing Coil Light and Power Issues

Hi everyone, I'm seeking help with my Audi A4 B8 2.0 TDI model experiencing a power loss issue. The vehicle displays a flashing P2564 fault code along with a blinking coil light and an illuminated engine warning light. I've already performed several diagnostics: the turbo system appears to be in good condition, and I recently replaced the Turbo Boost Control Position Sensor (TBCPS) — however, no improvement has been observed. I've inspected all connectors and wiring harnesses thoroughly; there are no visible signs of damage, fraying, or exposed wires. I also checked all vacuum hoses, which appear intact. However, the hose connected to the turbo is not drawing any air, suggesting a potential issue with the sensor or its electrical connection. To further diagnose, I disconnected the TBCPS electrical connector and used a digital multimeter to measure voltage at the sensor wiring harness. With the ignition key ON but engine OFF, the meter read 3 volts — matching the manufacturer's specifications. When I reconnected the sensor, the reading dropped to 0 volts. This inconsistent behavior strongly suggests an internal fault in the TBCPS sensor or a grounding issue. However, since replacing the sensor didn't resolve the problem, I'm wondering if there could be another underlying cause related to the P2564 code or electrical interference. Any insights or suggestions would be greatly appreciated — I'm currently out of troubleshooting options.