E350 P0657 code and transmission shift issues
This is a 6.0L diesel, 2005, which just had the EGR delete, new oil cooler, etc done on it by Gillette Diesel in Draper, UT. I drove it from SLC to ABQ with no issues. On the way back tonight the transmission began to not shift properly (would not shift into OD, would not down-shift when in town, even when putting the lever in 1, 2, etc). The issue seemed to resolve itself every time I shut it down and then re-started the engine.
A code reader at the local auto parts store showed P0657, which engine codes.com reveals as "The ECM has detected an interruption to the transmission control solenoids"
I don't know what or where to look. I am not mechanically inclined unfortunately. Can I continue to drive this thing tomorrow or I should I have it looked at ASAP. Fluids are clean and at proper levels (less than 3000 miles on a transmission flush).
It also had another code, P0401 but I am assuming this is due to the EGR delete.
Any help would be appreciated.