Engine not starting, Fuel pump control error

[brady.ie]

Hi,

I have a 2012 B7 Passat, 2.0 diesel with 160k miles.

The clutch was replaced a week ago and the car was driven home from the garage without issue, approx 70 miles - not sure if this has any link to my current issues.

In the days after, the Glowplug light would flash while driving and the car felt like it lost some power. Then earlier this week, the car cut out after approx. 200 meters drive from our house, it would turn over but would not start. It eventually started and I got it back home. Since then it has not been driven. It did start the following day, but cut out after a few seconds.

I completed some initial troubleshooting:
Download of codes shows P062700 - Fuel Pump “A” control - Circuit /Open.
The fuel lift pump in the fuel tank is not running when the ignition is switched on. I checked all fuses and all are ok. I swapped out the J27 (?) relay (it’s a 646 relay) with another one and still no difference. Wiring seems fine at the lift pump, but there is no voltage detected at it.

I’ve tested voltage at the J27 relay which feeds to the tank lift pump, pin 1 has +12V when ignition is turned on and for approx 30 seconds after the ignition is turned off.
Pin 2 reads +2V on it. It is not grounded and never seems to go to ground.
When I loop between pin 5 and pin 3 at the relay, the lift pump runs in the tank.

Should the lift pump run the whole time or does it just come on to prime the system?
And if it just primes the system, then what makes it cut out, is it just a timer or is there a pressure switch?
What could prevent the fuel relay from getting a signal to allow the pump to run?
What controls the signals to the J27 relay?

Just looking for a better understanding of the system so as I can try to narrow down the root cause of the issue.

Any suggestions as to what I should be checking?