I was recently asked to diag no reverse lights on a '99. I started by making sure the bulbs were OK. Oddly, Dodge opted for a dual filament 3157 which makes no sense to me. A 3156 won't fit, but isn't supposed to anyway.

Next I verified no power at the sockets using my PowerProbe. Make sure you've got key on and shifter in R.

I checked fuse #7 in the IC fuse panel but it was in good shape.

It appears Dodge switches power here and the purple/black is the power. Then I pulled the plug at the NSS. In R with key on, there was no power at the terminal which feeds the purple/black.

I propped a dollar store mirror so I could see a reverse bulb and applied power to the harness at the purple/black wire (this is where Power Probes are cool) and the reverse lights illuminated. Thus, wiring and bulbs are good.

I then determined the NSS was bad and a new one from O'Reilly did indeed fix the problem.

I should have made sure power was coming into the NSS ‐‐ even though I knew the fuse was good -- but I was rushed and got lucky because my diagnosis was ultimately correct

 

I never complain about good luck.