Service Technicians vs. Auto Mechanics

Brake light switch doesn't fit for the no steering or lack of communication problem so that can be ruled out right away.

No need for the coffee either, this has to be diagnosed in a half hour or less or you fail the class.

The next step is to find, with the schematic where the high and low CAN wires are in the OBDII connector. This is where you find out that the wires are not where the schematic says they are (not uncommon). So without another vehicle to check to see if it's wired right you look for the wire colors as noted in the schematic. You find that instead of being in terminals 3 and 9 they are in terminals 6 and 12.

With the battery diconnected you measure 0.7 ohms between the high and low CAN wires.

The CAN system uses two termination resistors wired in parallel in two different controllers that measure 120 ohms each. So what should you be reading when you measure the resistance at the OBDII plug?

This is going to tell you what the problem is but not where it's at yet.