Wipers stop in wrong position when shut off. Vertical instead of horizontal.

u need a new parkpawl witch is mounted on the wiper motor. wiper linkage connects to it.

Did the wipers stop in the up position? If so it may be a blown fuse or a defective wiper motor. Have you looked at the fuse-box? Did you mean that the wipers swipe the windshield correctly and then when the wipers shut off they stop in the wrong position. If this applies then inspect the wiper transmission. There could be worn/loose linkage between the wiper motor and the wiper arms. Also if the wiper motor was just installed. The clock position may be wrong. Please let me know if this information helps. If not please write back, leave more details, and I'll do my best, good luck.

BCM has nothing to do with this function , MMM - memory mirror module !
Memory Mirror System Operation
The MMM is capable of storing mirror position for 2 different drivers. Mirror position is determined by both horizontal and vertical position sensors in each of the power mirrors. The MMM supplies a reference voltage and a low reference to these sensors and determines mirror position through the horizontal and vertical position signal circuits.
The MMM receives power through the battery supply voltage circuit and the MIR/LOCK fuse and a constant ground source. Any time that battery voltage is disconnected and then connected from the MMM, the MMM will enter the mirror relearn mode. The mirror relearn mode can also be commanded using a scan tool. Refer to Memory Mirror Module Learn for further information.The memory switch receives power through the battery supply voltage circuit and the MIR/LOCK fuse. The MMM upon receipt of a memory switch signal input, a class 2 message from the SIC or a class 2 message from the PCM indicating that the transmission is in park, will then supply battery voltage and ground to the appropriate power mirror motors through the mirror motor control circuits to move the mirrors to the predetermined positions.

DTC B1586, B1596, B1616, or B1626
The mirror horizontal and vertical position sensors are potentiometers. The Memory Mirror Module (MMM) provides these sensors with a 5 volt reference circuit and a low reference circuit. The MMM monitors the horizontal and vertical position sensor signal circuits which change values based on mirror position. These voltage values are used to determine mirror position and can be set into memory. When the MMM receives a memory recall request, the MMM will control the power mirror to the memory position based on the horizontal and vertical position sensor signal values.

Install a scan tool.
Turn ON the ignition, with the engine OFF.
With the scan tool, observe the mirror horizontal and vertical position parameters in the Memory Mirror Module (MMM) data list.
Operate both the left and right mirrors through the full range of movements.
Does the scan tool indicate that the left and right mirror horizontal and vertical position parameters are within the specified range?

Memory Seat System Components
The memory seat system consists of the following components:
• Power seat switch assembly
• Memory recall switch assembly
• Horizontal adjuster motor
• Front vertical adjuster motor
• Rear vertical adjuster motor
• Recline adjuster motor
• Memory seat module
• Memory mirror module
• SEAT 25A circuit breaker
• MIR/LOCK 3A fuse

Your best bet , take it to a qualified repair shop !

apparently, something inside the wiper motor spun and now it thinks the down position is the up position.

a new wiper motor is my only suggestion since the sensors/controls in these motors arent user serviceable.

Good luck and be careful!

possible nut holding mech. is slightly loose or stripped.

If the wipers end up in the vertical position and they are the HIDE type usually its the park mechanism mounted on top of the wiper motor that the linkage attaches to, there is a small spring loaded lever on the bottom of this device that wears out and fails to activate the PARK position proccess when the wipers are turned off. When the wipers turn off the motor reverses and the lever is meant to catch on a tab and compress the mechanism pulling the wipers to the park position. Only thing I know what to do is replace this mechanism, ($150. new 25. used)

You will need to replace the wiper transmission.This is a common problem.

This is an easy fix. Likely ice got on your windshield and froze your wipers to the glass then when turned on moved out of position. Take the cover off the base of the wipers and loosen the bolts. Put them down all the way and tighten. When wipers are turned on when frozen to glass the gears want to move but cant and loosens at the base. Please let me know if this does not help and will look into it further but this is probably it. Thanks

the "horizontal park" mechanism is in the actual wiper motor assy.

You will need to replace the wiper motor. Most likely the circuit board is bad. You might check with your local chevy dealer and see if there is a recall on the wiper motor before you buy a new one, even if you are not the original owner the car the recall will still be done free of charge. Some chevy models did have a wiper recall. I hope this helps.