From what I know , the di pumps cannot be part-able or fixed ... They need to be re-done or rebuilt and calibrated as a whole.
Most codes relating to pumps usually end up being the pump swap over.

I hope I am wrong but I know two people who were in the same boat and just couldn't get rid of the patrol after sinking so much $ into it so they just paid up and got the pump replaced.

And they are not cheap.
$3-4k for a reco. Unit.

Try ringing wreckers , get some prices.

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