1998 GMC Class 2 Communication / ECM issue

[SullyGMC]

Need a Top Gun Mechanic to work on my West Coast 1998 GMC Sierra K 1500 .. have a class 2 data communication problem , along a ECM code have the following codes PO605, UN1026, UN1042, UN1064, and UN1193, my cluster gauges are all off (not the cluster) , miss fire on cyl #4 ECM has been swapped out no difference ..  When I got it the dash showed a SRS light , had no horn,  replaced the clock spring ,have horn now , dash light went to just a airbag light . took this to a shop they had 4 hours in labor and found all my grounds and power supply were good , cluster was tested at United Radio tested good, they could not communicate with the airbag module. replaced airbag module airbag light is gone . Still have the above codes.   speedometer off by 8 mph faster , volt gauge only shows 10 amp (confirmed charging at 13.9 to 14.0) temp gauges shows 240 actually temp is 180- 195..  any help would be awesome !! Thx !!

[Brian Lindsey]

contact ivan at pine hollow auto diagnostics in state college , pa. or try eric at  south main auto in avoca , n.y. , both have youtube channels and are great at elect problems