OBDII scan is receiving NO BUS CODE?

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This is received many a times while scanning error codes from cars ECM.
Most of the time a no bus comunication problem is due to a short to ground or a short to power on the bus wiring. The bus wiring is a pair of wires that connect all of the modules in the vehicle togather so they can all comunicate, kind of like a telephone wire set that allows calls from one module to the next. If you short it, then the electrical signal can't get to the destination module (no bus).
The voltage should be about 2.5 volts. The voltage is usually created by one or more of the modules, so if one module fails but doesn't short to power or ground the other modules can still communicate with the scanner and tell the tech where the problems lies.
If it is 0 it is shorted to ground (this means the wire has shaffed and touched bare (ground) metal somewhere, or a module has malfunctioned internally and grounded the curcuit), if it has 12 volts, then it is shorted to power and this is usually a bad module.
The best way to test is to actually unplug modules one at a time untill the bus comes to life again. Then you know which module it is. If it not a module then it is a bigger diag job.
Just as a side note, most of the time we run into this type of problem it is usually the radio or the heater control head. To test these simply unplug them one at a time and see if the scanner now reads the bus.
This basic details will help.
Few diagnostic code error solutions:---

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