Q: My car won't start. The odometer reads: NO BUS.

The error code "no bus" means the PCMS are not communicating with each other. Likely one of them has gone bad, or there is a bad connection. You can do further testing on them using a multimeter. This will require a diagram and detailed information on the specifications the units must meet. This would involve testing the input and output voltage values on the PCMs to determine which one is having issues. If you need assistance with this, have a certified technician, such as one from YourMechanic, come to your location and diagnose the starting issue firsthand. Best of luck.