Lights on Dash flicker

All the cluster lamps are on the same lighting circuit, it may have a bad connection at its connector. This is a big complaint. The only thing you can do is remove this cluster(as its called) turn it over and check these connectors. Also there are ground straps on each side of the dashboard. They can be loose or need cleaning. Their behind the lower kick panel trim. Big problem. Everything uses a module that can also have internal problems. Your headlamp switch could also be bad.
In a 2005 mini-van, the dashboard is the total front support for its interior and mounting points for quite a few different parts. I'll refer to your part, which flickers as it is called a 'cluster'. The illumination for both odometer and gear selection indicator are both part of the cluster driver which also controls all the other gauges as well as warning lights and triggers chimes for audible alerts. The first step would be to try and duplicate the problem, on either a roadtest, or inside, where the lamps(lights) can better be seen. If moving the area does not cause any flickering it would be best to switch on the headlamps, and see if that control also can be used to duplicate this annoying problem. After this I would hit the schematics. After taking a good look at the circuits involved, a computer tester was used for checking any stored codes. If none are present, and the same problem could not be duplicated, the grounds and power circuit wiring, relays, and module locations were also looked at, all in an attempt to find exactly what is good, not bad. It is a process of elimination. The cluster contains all the gauge drivers, and this module gets commands from another module, called a body control module, this gives you many more areas of concern. But if only the odometer and illumination circuitry is involved, it can't be too many things. The cluster ground is on the left side of the instrument panel, usually next to the parking brake lever. You may need to remove one, two, or 3 trim panels just to make sure it is clean and tight. The power for this circuit(wires) is from the engine intelligent powerr module. So these are the power and ground circuits for both. The body computer is located on the left side near this ground I spoke of. It is involved with everything inside the body that uses any switch you may select. So whether its the BCM, cluster driver, or loose ground or power wire is part of a technicians job if no stored codes are present. I think your headlamp switch or cluster connection or module drivers are loose internally. You can remove a couple screws to access the cluster, look at how its connected, the small pin terminals can be sqeezed with a tiny dental pick. Other than this the cluster module is replaced. Much has to do with all the other wires and loads that the illumination wires control with the headlamp dimmer. If you decide to look for this problem, just let me know. I'll help you to select the proper tools and information. Don't have to thank me, its the men and women who created this website who have made all this possible, thank them. And good luck, of course.

Can you please shoot a quick video with your phone so we can see what's going on, that would be great. You can upload it here with your response.