I have a 2004 Nissan Quest that needed a new transmission mount. Everything listed next was working fine before I started working on it. When I finished and started to test drive it, the following things don't work anymore: Display Unit, A/C & Heating controls, and radio controls. The check engine light had been on before I started, so I took the van to a parts store to pull the codes. They tried 2 different OBD II devices and neither could pull the codes. The second device acted like the car wasn't even on, even though the key was. I took the van to a second parts store and they couldn't pull the codes and said it wasn't even connecting to the car, so I assume the port is bad too. An interesting thing happened while working on the van: I forgot to disconnect the battery before starting to work and when my wrench hit the transmission, I saw a spark. I disconnected the battery and finished the job. I've checked continuity on all the fuses and they all check out fine.

What should I check next? What could have caused these things to go out and how can I fix it?

Thanks for your feedback.

1. Check the fuses
2. Check the ground points
chances are this is just a burnt fuse. pull all of them one after another and check with an ohmmeter.

It's all fixed! Earlier, I checked all the fuses for continuity with a multimeter while they were plugged in. Today, I decided to pull each fuse and inspect visually. The 15A "Electronic Parts" fuse was blown. I replaced it and everything is working again. I don't know why one fuse can take down so much and I still don't know how the fuse passed continuity when plugged in, but it's fixed.