Check Engine Light (CEL): Eurovan

The check engine light can come on for about 6,000 different reasons. The most common reason is forgetting to put the fuel cap back on, which makes it impossible for the evaporative control system to work properly, and causes the check engine light (CEL) to come on. In 1997-2000 Eurovans that still use ignition wires (01-03 models do not), misfire codes are very common.  
Whatever the reason your CEL came on, you might think, "Heck, it runs fine, I will just ignore it.  When it's time to smog it, I will have it reset, smog it, and forget about it again." Unfortunately,  having the light reset does not mean you can just go in and have it smogged before it comes back on. That would be great, except that after the light is reset, the vehicle has to be driven a certain amount of time and miles and heat cycles and at certain speeds (the exact amount of each is a mystery only the BOSCH engineer that programmed it knows for sure) before the computer goes into the "all-good, ready for smog" mode, commonly referred to as "readiness." On top of that, the light is like the boy who cried wolf: It may indeed be telling you something more serious is wrong—or it may not. So, no, it is not a good idea (in general) to just ignore the light.
We sold a 1997 Eurovan to Liz and Terry back in 2005. By the time they got home about 250 miles away, the check engine light was on, and the code was "random misfire." We had done a complete service on it, but did not replace the ignition wires. This had happened to us once before already, so now we ALWAYS put new wires on every 2000 and older EVC we sell or service (as stated above, 2001-2003 models don't have ignition wires, but instead each spark plug has its own coil right on top—this "coil on plug" is a way better system, and pretty much used universally by all manufacturers today). We sent a shop in her area a set of wires, paid them to put them in, reset the light and all was good... for a while.  We paid the shop for hours and hours of time, over an 18-month period to replace the wires, plugs, injectors, coil pack, engine management computer (ECU)—you name it. They could not get the light to stay off long enough for the computer to go into the "all clear" mode so she could smog the damn thing. Finally I said, "Terry, I am sorry, but you have to bring it back to us." So, they bring it back, hop on a train, and head home.
We gave the job to our senior tech, a forty-year VW veteran extraordinaire. He opened the hood, snapped in two loose spark plug wires that were not on all the way, reset the light, and voila. We drove it around until the computer was ready, smogged it, and that was that. As far as we know, the dreaded light has remained dark... and we'll take that as a small victory!
So, was it one of the other components, perhaps? No, because all the stuff we sent them to try came out of other Eurovans into which we plugged in the suspect parts that came off of Liz's Eurovan, and they worked fine in the other Eurovans. (We have lots of Eurovans around in various stages of restoration, being prepped for sale.  Don't worry, we did not steal a part from your Eurovan while it was here getting worked on!  We wouldn't do that... probably.). No, it was probably just a loose wire all along.
So, was that other shop just totally incompetent or what? I don't think so, because they seemed really sharp. It just gets to a point where you just can't see the forest for the trees. It is just human nature to think that, when you have done something, and paid close attention, there is NO WAY that could be it. But in this case, it was. On top of that, there are some aftermarket, very high-quality ignition wires out there for the VW VR6 engine that work great in Jettas, Golfs, Passats and other VW models fitted with this same engine, but are just too short for the Eurovan application. You have to get the right ones (which, of course, GoWesty has). The VW dealer has correct wires, too. But if you have a misfire code and go to a VW dealer, they will replace one wire at a time. Needless to say, that can get kinda pricey. For some incredibly unbelievable and stupid reason, VW has always sold ignition wires individually. I don't know if it's a liability thing—like they can't sell someone anything more than they actually need, or they get sued? Dealers have created such a bad name for themselves, with so many highly publicized fiascos, I guess they just have to cover their asses? I don't know why for sure, but I do know that it's ridiculous to replace ONE ignition wire at a time.
So, the moral of the story: Keep it simple. Tens of thousands of these vehicle were produced in exactly the same way. It is probably NOT something super complicated or unusual, but most likely human error or a maintenance item. Just like on a Vanagon, or any other vehicle for that matter, first make sure ALL the regular maintenance stuff is doneplugs, wires, filters, fluidsstuff that doesn't last forever anyway, and that it's probably time for you to replace. But, of course, you have to put on quality stuff and put it on CORRECTLY. If you get burned out, have someone else check your work—we always recommend a professional shop.