2005 Mercedes Sprinter 2.7L Turbo Diesel P0106 Fault - Persistent Code in Limp Mode

I own a 2005 Mercedes-Benz Sprinter 2.7L turbo diesel engine with over 450,000 miles. The vehicle has stored seven diagnostic trouble codes and is currently operating in limp mode. I have successfully resolved all but one code: P0106. After replacing five glow plugs (code cleared), the MAF sensor (code cleared), camshaft position sensor (code cleared), and MAP sensor (code cleared), the engine no longer exhibits hard starts. However, the P010 or P0106 code persists. I recently replaced the turbocharger with a new unit including actuator and resonator — the turbo noise is now gone. The intercooler and all associated hoses were pressure-tested for leaks; no issues detected. A fresh air filter was also installed. Despite these efforts, the P0106 code remains. Live data shows: ETC = 169, MAP = 29.2, IAT = 111, MAF = 11.6. The PCM reports a signal voltage of 4.5V for the intake manifold pressure sensor, but only a ground signal is detected — source voltage reads 1.4 volts. This indicates an inconsistent or faulty signal from the sensor to the Powertrain Control Module (PCM). I am out of conventional fixes and seeking advice on how to diagnose or resolve this persistent P0106 code in my 2005 Sprinter diesel engine.