Technical Ducato error code

[RooferAgs]

Hi all. New to the forum. 2014 Fiat Ducato 130 multijet tipper. Currently have error code P0089-78 Fuel pressure system-Alignment or adjustment incorrect. Mechanic says fuel pressure ok. Checked all wires for chaffing and connections. Vehicle currently in limp mode. Vehicle tends to jump out of hill holder and beeps up on the dash 'hill holder unavailable check engine'. Also esc light comes on. Will then clear at next start until it does it again. Also occasionally chucks out smoke. Any ideas before main dealer takes a look?? Thanks in advance.