Hey guys, workin on an 08 chevy topkick/c series ambulance with an lmm. Showed up customer said truck would not go over 45, speedometer doesn't work and check engine light. I pull it in, hook up my Mac scanner and find a u1000, u0101 and u0106. 1 was ECM lost communication to tcm, next was ECM lost communication to glow plug module and the other was stored in the tcm saying lost communication with ECM. I busted out the wiring schematic and found all 3 modules are on the GMLAN line wondering if anyone has ever had this issue, maybe a terminating resistor issue? Or a failed tcm? Gonna start tomorrow with ohming data link wires from each module but if I find nothing wrong with wires what would be the best way to rule out and pinpoint individual modules. Thanks for any help.