Part#

[Barry Nave]

For the optosensor.
I'm willing to give this a try for the code 35 issue.

[twaddle]

How about contacting your nearest Stanadyne dealer for a price.
While they are giving you the price ask them to leave you the part number to save time when ordering.

Regards

Jim twaddle
Biggar, Scotland

[Kennedy]

I would just drive it and ignore it. Roger P drove I don't know how many 10's of thousands of miles with his truck doing this. He even won a NEW DS4 pump in a drawing at the Rendezvous back in like 2001. Kept driving with the old pump for quite some time (years) as I recall.

[Barry Nave]

Black tape over SES. Gotya :D