VW Passat B6 TDI 2.0 - P0670 Fault: Engine Management Light On, Cold Start Issues, Glow Plug Relay & ECU Diagnosis

Hi everyone, I'm currently experiencing a persistent fault code P0670 on my VW Passat B6 TDI 2.0 (R4 2.0L PPD1.5 G). The issue is causing the engine management light to stay illuminated constantly — it sometimes turns off during operation but returns after each engine restart. In colder weather, especially in winter, the car occasionally fails to start on the first attempt, which has been frustrating and concerning. I've already checked the glow plugs, and all appear functional. My mechanic suggested checking the Glow Plug Relay (Part No: 0281003038), but I'm now wondering if this P0670 code is actually related to the Engine Control Unit (ECU) — specifically model 03G906018CE. Below is my OBD-Eleven scan log for reference: ---------------------------------------------------------- 01 Engine: System description: R4 2.0L PPD1.5 G Software number: 03G906018CE Software version: 9384 Hardware number: 03G906018CE Serial number: VWZCZ000000000 Coding: 0000078 Trouble codes: P0670 - Glow Plug Module Control Circuit Short to B+ Status: Passive 33 OBD-II: Trouble codes: P0670 - Glow Plug Module Control Circuit Status: Passive ---------------------------------------------------------- I'm seeking advice on whether the P0670 code points directly to a faulty glow plug module, a wiring issue, or a deeper ECU software/hardware problem. Any experience with this specific fault in Passat B6 TDI 2.0 models would be greatly appreciated. Thank you for your time and insights! Best regards, [User Name]