Astra 2011 2.0 Fault Codes - P0087 & P0399 - Cylinder 1 Pressure Circuit Malfunction

[coalfield]

Have the 'Service Soon' message popping up intermittent on my Astra J 2001 2.0 Diesel, and the fault codes read are:

P0087 - Fuel Rail - Too Low Pressure - Unrecognised State
P0399 - Cylinder 1 Pressure Sensor Circuit - Malfunction - Faulty Function

The car  seems to drive OK, no general loss in power but am noticing when changing gears the engine revs seem to overun if the gas is less off when the clutch is down.  i.e. if chaning at 3,000 rev, and i put the clutch down and let off the gas, the 3,000 revs is maintained for a few seconds and not inline with letting off the gas.  Not sure if this is linked.

Any advise in tracking down the issue appreciated!

[Rusty2009]

These cars do hold the revs for gear changes.

Is there any byte code to go with them codes?

P0087 = https://workshop-manuals.com/vauxhall/as...p0088_lbs/

P0399 = https://workshop-manuals.com/vauxhall/as..._or_p03bb/

Also we have quite a long list already made for errors.
https://www.vxoc.org.uk/forum/Thread-Fault-Codes

[coalfield]

Thanks will have a look there, I am guessing Glowplug 1 may need replacing and hopefully that sorts
I unfortunately dont have any byte codes :(