I see there have been a few of these issues, one I think is probably the same issue as me but beyond getting this fixed, I really want to know how this circuit works so if you understand this, please enlighten me because based on the schematic, my symptom should not be able to happen. For reference I am looking at Figure 13.1 in the may 2004 electrical guide

For normal wiper operation it seems that the wiper park relay is the key to the whole process, when it gets energized, power goes from "54" (which I believe to be fuse 12) then goes to the input of the high low relay and power is provided to the motor and wipers move
When wiper park relay de-energizes and if and only if the wiper is off of home, then the wipers get powered from powerpoint 56 up until the wiper reaches home and then wiper stops.

My symptom is that all the wiper functions seem to work except the park. For instance if I pull back on the stalk which would normally be 1 cycle, I instead get about 2 and a half cycles and then it stops wherever it happens to stop (I say 2 and a half because that is usually what I get 2 full cycles plus around a half, sometimes slightly less than half. If I set to low or high all works well until you turn off the wipers in which they will continue to move for a few cycles and stop randomly. If I use intermittent, the cycle begins but instead of a single cycle, I get a few then no consistent park

My thought is for a single cycle to really work, the park relay should only be energized enough for the wiper to move from home and then allow the autopark mechanism to take over from there(I could very well be wrong)

The other person with a symptom very similar to mine ended up being a bad connection somewhere between fh17-4 to live voltage and I suspect I have the same issue but haven't dragged out my meter quite yet.

I have so far replaced the motor (based on experience where non parking is almost always a failure of the internal home switch, my bad for not knowing newer cars would be different. I have also swtiched around relays with no change in symptoms. I do notice that I don't have all the relays mentioned in 13.1 but I'm guessing that is just bad numbering in the electrical guide.

I suspect I have two issue (without measufing yet) I suspect I am getting a too long of a pulse on the park relay as well as no consistent voltage from '56' thus making park not work

 

OK, got the meter out, definitely no voltage on FH17-4.

Now the task is to decide if I am going to try and chase down the break or just cheat and run a new wire. This is a pretty low featured V6 model so I have all kinds of available jumper points in the under hood fuse panel I just hate to do an inline fuse connector when there is a perfectly good fusebox there.

Not sure it explains the extra rotations for a mist operation, I really would have thought it would barely move but I'm willing to live with that if it remains.

There is another s-type at my local pull a part, I might go experiment there and see how many miles that wire routes from the fusebox to the wiper motor. It is only a foot or 2 away, I figure that means the factory used 20 or so feet of harness :-)

 

FH17-4 is connected to fuse F12 (20A) along with the unswitched power to the two wiper relays R15 and R16, as well as the power wash relay R18, but you may do not have that on your car. It is strange that only one wire has failed.
If you do fit a bypass wire make sure it is fused.
As you may well have spotted by now lots of the non switched 12v wires are brown with a red stripe.

Mellow

 

Hmm, it's very rare to have a broken wire. Not impossible, of course, but also not very likely, especially if the harness is in a protected location.

Power to FH17-4 comes from fuse F12 in the front power distribution box. This is direct battery power, always hot. That same fuse also feeds power to three other spots in the washer system. Look at legends 53, 54, and 55 (all labeled in boxes) in figures 01.2 and 13.1. This is in addition to legend 56 feeding your FH17-4.

To isolate the break, also check for power at the following locations:

Relay R16 socket #1 (legend 53)
Relay R16 socket #5 (legend 54)
Relay R15 socket #1 (legend 55)

Depending which of these 4 locations do or don't have power, you should be able to isolate the break. You could also remove the fuse (F12) and look for power at the two fuse sockets. One will always be hot and is the "upstream" side. The "downstream" socket should not have power and is connected to the four points mentioned above, via splice FHS57 and connector FH32 pin 32.

What is access like under the power distribution box? Can you unbolt the box and lift it up a little? Rather than jury rig an extra wire, I'd much rather isolate the exact fault and repair it. If access is marginal, and a new wire is needed, I'd still rather tie into the original power source versus tapping into who knows where.

 

Sorry for delay in answering but I just lived with this over winter last year and finally got back to it this summer in prep for the next winter :-)

So all functions powered by F12 work except the park relay so it must have been a broken wire in that harness going to motor(56 in diagram). I did not want to take entire car apart to look along the length of that harness so I attached an inline fuse to unused power pin (lower feature car so I had a ton of unsed slots in that front fuse box) and ran that fused wire right to the motor at FH17-4. As soon as I hooked it up the wipers parked and all has worked since then. Such an oddball circuit, with power traversing through both relays (I mean the high low relay actually gets the high current from the park relay either directly (54) or when the park run switch is activated (56). I miss my 3 wire wipers but then I guess we wouldn't have that super cool wipe one more time a few seconds after the wash operation (or could we?)

One thing worth mentioning is this car has had an air bag deploy so maybe the collision chafed a wire and in my 3 winters I have had it finally corroded it all the way. Can't wait to see what electical gremlin pops up next.