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Ohm test won't tell you anything. Never use that unless you are actually testing a resistive device or circuit such as an incandescent light bulb, a relay coil, or an actual resistor. Ohm setting on your meter is COMPLETELY USELESS for the vast majority of troubleshooting you will do for wiring connection problems. Forget it exists (unless you actually need it).
You need to perform a Voltage Drop Test. Here is one video - there are many more. Do a search and watch videos till it makes sense:
So you have the warning lamp chase sequence going? That means the annunciator panel isn't connected to the MMDC via it's internal CANBUS. That is most probably a power supply issue or low voltage issue, etc. Unless other things have been touched since it worked last?
How long has the truck sat this time? Are you absolutely sure the batteries are good and FULLY CHARGED? Check that FIRST and the battery connections. If you are SURE that is good start by checking all the breakers (or fuses). And then check that you have power at both the input and outputs of the 12v and 24v ignition relays under the PDP. You can access them between the PDP modules if you are careful. They are big relays with big wires and supply 12v and 24v ignition switched power to power up all the ignition switched circuits in the PDP modules.
