Hi @markfragola
Here's the [document|41920|service manual] for the washer that may help.
The fault codes posted by you seem to indicate a problem with multiple components e.g. drain pump (even though you've replaced it), pressure sensor, water inlet valves, lid lock etc.
Maybe start on p.74 (p.75 of 83 pdf) of the manual and follow the checks for a fault code 18.
If you find the problem and it is a faulty part that needs replacing, here's a [https://www.searspartsdirect.com/model/3eo9behey7-000432/ge-gfw850spn5rs-washer-parts|parts list] that is useful. Locate the wanted part in the list and note the part number for the part that is shown with it. Search online for the ''part number only,'' to find suppliers that suit you best.