My 1998 Dodge Caravan has a service engine soon light on.

Call your local Dodge dealership, they may have a solution.

Something you thought up

po420 is catalytic converter efficiency. You will have to replace it to keep the light off. But as long as you live in a state that doesnt require emission test you can ignore it and it won't effect the way the van runs

If you want to do it by yourself, I strongly recommend you to buy a manual book because there is a built-in self dianostic Check Engine light codes. And how to do it, just insert the key into the ignition and do it three times, Turn On and Off the switch but don't start the engine, and you will see the check engine blinking. Count the blink and start with 1-2 blinks, the next blink is to tells you where is the problem and it will end to 5-5 blinks.(BLINK is the CODE) and you could check in the book. If you know somebody has an OBDII Scan/Diag.,thats will be easy. ok

Your Caravan has no rear differential. The van is a front wheel drive, you may have a bad brake or your spare tire under the back of the van is lose. the other thing to look for in the back is the rear shocks could be broken or lose. Good luck and keep me posted, be glad to help get your van running 100% again soon. 

back wiper and recirvent light constanly flash when started

The procedure for re-setting the HVAC control panel on a 1998 Dodge Grand Caravan follows:
With ignition on but not running
1. turn knob to air vents
2. turn fan knob to ON
3. temperature setting on COLD (2X) {I have dual temp controls}
4. hold top(rear wiper) and bottom (rear wiper with wash) buttons pressing down together until all the buttons cycle through (this will require 1 to 2 minutes of continuous pressing)
I learned this from a very helpful local Dodge service adviser

You would have to repeat the problem with the scanner hooked up and someone who knows what he's doing watching it. If the check engine light came on then a code will be stored.

( times out of 10 Hun its the Timein on it take it in for a Tune uP or get the Timin light and do it your Self

It comes on when the key is turned on to show it works, then it goes out as soon as the engine is started, it has a fuse, that will be marked, if the fuse is ok then you may have either a bad connection at the cluster connector or a bad ECM