Vauxhall Vivaro cold start issues

Could possibly be faulty engine coolant temp sensor and not sending correct info to ECU .Check power to and operation of glow plugs . Carry out a diagnostic check with a good scanner that covers all systems / modules for fault codes

I was checking various things and have some more information on the fault, I will start with glow plugs - I checked with multimeter the resistance value on the plugs and it is around 1.8 Ohm so that would indicate they are in good condition? I also checked the voltage on the glowplug caps - once i turn on the ignition there is a spike to 12V and after about 1 second it drops and stay at around 1-2V, ambient temperature at the time was above 10C, could it be that 1 second is enough to warm up the plug to required temperature? I also checked the glow plug relay near the battery - pins are intact and sparkling clean. Today I had a mechanic plug in diagnostic computer and checked fault codes, 3 popped up - P0380 ( Glow plug/heater circuit A), P0107 (Manifold Absolute Pressure/BARO Sensor Low) and P0098 (Intake Air Temperature Sensor 2 Circuit High (Bank 1). On a quick google check first code would point to glow plugs or control module - I assume this error code would be most probable cause to starting issues? New module itself is quite pricey, question would be - are there any other tests I could conduct on glow plugs to verify that they are indeed not the cause of the issue and are working ok? Could other 2 codes also be responsible?

Your van powertrain control module (PCM) depends on correct readings from the sensor’s to determine the right amount of fuel needed and to inject into the engine cylinders.