When I get in the minivan before to start the engine interior ligths start to flash and dashboard lights flicker when engine is running and lights are on

Could be the alternator with a bad or failing diode or a bad phase,there are 3 phases making AC which is converted to DC.
Supply your own field power to the alt with the regulator unplugged.Lights still flickering?replace alt.

Open each door (one at a time) with the car running and parked.
Look for the small contact switch that tells the car the door is open/shut.
See image for location.
Press that switch in firmly and watch the dash to see if the light comes on while you are pressing.
This will tell you which one of the switches is bad.

charge or replace the battery.

Sounds like a very low battery to me. You need to have your battery and charging sytem checked.

engine check light. needs a computer scan and check. needs a workshop.

Check to ensure that battery cables are tight, and engine ground, and all wires running to your alternator.

Wow. Ok. That was a pretty rude response you received there form r_clark. Let's see if we can find a reasonable way to help you.

When you first get in your car, instead of starting it right up, turn the key to the "on (or run)" position. With the key on, but the engine off, most of your warning lights will light up and stay lit. Some may go off after a few seconds. Draw a quick sketch of the layout of your dashboard before doing this. Then, with the warning lights all on, jot the name and location of each one on your sketch. The next time you are driving, when the light flickers on and off, you should have a fair idea of what it is.

Also, if you are in the process of actually starting the car when this happens, keep in mind that when you turn the key through "on" to "start" and then release it, the vehicle's self test for the dash will turn all those warning lights on, then off, briefly. Certain important lights will come on last and only flicker on briefly. As long as they are doing that during start up, they are ok, and it just means the lights are working properly. If they are actually flickering on while driving or idling, then you have a problem, but likely not a serious one yet.

Hope this is helpful, good luck, and let me know how it works out!

I work for honda and have seen this often. Mostly on the newer vehicles (2008 and newer). we have always fixed this by replacing the insterment cluster. expensive yes but always fixed it. it in itself is a seperate computer so when it is replaced it will need to be initalized through the HDS

Could be a bad light switch or relay, but I'd check dash and body grounding first. On every Jeep I've ever owned, I run a direct ground to everything before I even drive it. To do this, Attach a 12ga or larger wire to the battery ground connector. Run that wire around the firewall side of the engine bay, removing insulation at several points and attaching the exposed wire to the firewall, (using short, self-tapping screws) both fenders and ground points for the computer. I also attach one additional leg which runs through the firewall (careful not to drill through anything important) and attaches to the metal frame of the dashboard. I also add a second ground wire directly to the engine block, eliminating any possibility of a poor ground anywhere. It sounds like a big job but it's not, and doing this precludes many frustrating and unnecessary problems down the road!

there is a short somewhere you will have to remove the dash and investigate