2004 vw jetta tdi code p0230

I have a 2004 vw jetta tdi and the check engine light came on. We have changed the feul pump relay, glow plug relay and cleaned the mass air flow sensor but the light continues to stay on. The code stays the same p0230. Any ideas?

Did you do a reset/clear code?

Did you do a reset/clear code?

Yes we reset it

How about fuel pressure, or fuel filter!

The car starts and runs fine. How would I check the feul pressure to see if that is it?