1. 1998 Caravan. Approaching 170,000 miles.
2. I have the phantom front windshield wiper problem. Symptoms: wipers will come on and stay on in delayed/low mode even when wiper switch is in the off position and until the ignition key is turned off.
3. I have replaced with new parts: both relays (hi/low & on), wiper motor, and multifunction wiper switch. (I normally don’t throw money at parts to solve problems but all these new parts were discounted/on sale.
4. I’m identifying and cleaning all the grounds I can find. So far I’ve cleaned the 2 ground wires that are attached to the transmission dipstick holder bolt. I’ve also run a separate ground wire from the windshield wiper motor to the battery ground.
5. I have a copy of and have followed Technical Service Bulletin #08-31-98 Rev A, even though my van is a 1998 model year. This did not help me find the problem.
6. I also have a set of Chrysler shop manuals to include the “Body Diagnostic Procedures Manual” and the “Service Manual” for the 1998 model year. And I have found and followed all the troubleshooting directions both manuals contain that apply to windshield wiper malfunction.
7. I have now made it to the last troubleshooting flowchart in the “Body Diagnostics Procedures Manual” where I disconnected the Body Control Module connection (grey) and found little resistance between the “Cavity C”in the on/off relay connection to a ground. The manual at this point says I have to “Repair the front wiper on/off relay control for a short to ground.”
8. I interpret these instructions to mean that the red/violet wire between the BCM and the wiper on/off relay has a short in it.
9. Am I correct in understanding that if I replace this red/violet wire that the wiper phantom problem will be solved?
10. One more big thing: I can’t be the only one who is hanging on to a couple of 3rd generation Chrysler minivans. An Achilles Heal for these is the problem and a possible accompanying BCM problem. Yet i have not been able to identify anyone reputable who can rebuild these BCM’s. Any suggestions? I’d even consider using a DYI source and make the repair(s) myself.
11. Comments?

 

I also am "hanging on" to my 1997 Grand Caravan LE w/3.3L V6. Currently has about 118K miles.
I have had the phantom wiper issue since we've owned the van (new) but usually it just randomly fires off the wipers one time then they shut off (and Park, I believe)
I never was able to determine exactly what caused the issue (e.g. sometimes it happens even when I didn't even touch the turn signal stalk).
Maybe soon I'll also see issue like you described (where the wipers stay on in low/intermittent for longer period, which would be a more annoying issue)
It sounds like you have done a lot of investigation on this issue...
I also have TSB 08-31-98 Rev A (Dated July 24, 1998) and it says it applies to 1996-1997 models (and I agree it makes sense to check that for your 1998).
It lists 3 symptoms...and it also lists the park switch circuit for the wipers. (#1 item for symptom #3) but you didn't mention that in your list of things checked (or changed). I don't have the "Body Diagnostics Procedures Manual"... and Sorry I don't have answer for your question in your #9.
I would not want to change a BCM for this.
I have done my own repairs on the ECM for my 1995 honda accord (bad/leaking capacitors and an open via connection from one side of board to the other),
fixed problems with Honda instrument cluster , and recently found /repaired a bad surface mount pullup resistor on my Caravan's HVAC control board
but with the Caravan's PCM, the entire circuit board is potted in a urethane or silicon jelly so it would be very difficult to diagnose or repair!
I have not checked the BCM but I suspect it's similar, unfortunately.


PS:
Looking at the Chrysler Service manual wiring diagram for the Wipers (8W-53-2),
I didn't see the red/violet wire you mentioned, but I would be suspicious of C1 pin 41 (Ckt V7, DG/WT, wiper park switch sense) into the BCM
(maybe the park sense switch is not making good connection so the BCM thinks the wipers need to be run to park them?).
Also the C2 pin 7 (Ckt V52, DG/YL) front wiper switch mux into the BCM comes from a big resistor network with a lot of different positions
so I suspect the BCM needs to decode a bunch of different voltages to decide what position the switch is in.
Given the large number of positions on that switch, it could be a difficult task for the BCM given that design....just saying.

 

Trying to delete a back-to-back post.. don't see how to completely remove my follow-on post. sorry.