Envoy 4WD V8-5.3L VIN M (2005)
interpreted as a "heartbeat" of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual
device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.
The following modules are connected to the high speed GMLAN serial data communication circuits:
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The transmission control module (TCM)
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The engine control module (ECM)
The interaction between high speed GMLAN and class 2 is assured by ECM, which acts as a gateway between the links.
