As mentioned apollo18's truck is most likely not CANBUS but GM Class2 Serial Comms, two entirely different communication systems not to confuse two terminologies. CanBus was only introduced for 2006/7 Model Years and later.

There are many YT videos on GM Class2, is quite informative and representative of the Hummer e.g. Splice Packs and voltages, which might provide clues as to what's going on with the vehicle/scan tool.

GM Class2 is a 1-wire bus system requiring only a signal and ground to communicate, +12V is used to power peripheral devices such as a Scan Tool. Any interference on the bus can affect the whole system.

CANBUS is effectively a 2-wire system with CanH and CanL which are differentially driven signals i.e. communication is based on voltage differences between two lines, rather than a single signal and ground, so CANBUS it's more resilient to electrical noise.

Any technology that generates noise can affect communications, although it's likely to be something connected directly to the signal line, or closely coupled to the +12V line going to the ODB2 connector. Connecting a Scan Tool to a different +12V source could also introduce issues, but where noise is concerned it is not an exact science.

Scan Tools use various semiconductor chip technologies to read the signal bus, some chips are more resilient than others. For example H2 control modules use different chips, but all meet the GM Class2 Specs which is why the Tech2 Tool is the scanner of choice.

Personally I'd prove my Scan Too (Diablo or Android) works on similar H2's or get truck scanned by someone else before getting into it deeper. Alternatively I'd connect a scope and check the bus etc.

 

thx for all the help yalll ill test this weekend and for sure relay my findings