How are the adjustable mirrors powered? mine stopped working

James,

Here's some sites that will help you...

https://www.google.com/search?q=driver+side+power+seat+on+2003+navigator+not+working

Best to you.

Hi Michelle , what make model an year vehicle ? On some vehicles this is function is controlled by a door module .

In order to control outside rearview mirror operations, as well as other door functions, the front door modules must be powered up. For this purpose, battery voltage is supplied from the rear fuse block, through separate circuits, to each front door module. Each front door module is separately grounded through a ground stake. The front door modules also use these power and ground supplies to drive the mirror motors, and to provide power and ground to window and lock switches and door lock actuators. In addition, the driver door module (DDM) uses these power and ground supplies to power the driver door switch assembly (DDSA) and integral mirror control switches.
Could have DTC'S - diagnostic trouble codes stored in BCM - body control module .
DTC B1544 01: Mirror Motors Common Circuit Short to Voltage
DTC B1544 02: Mirror Motors Common Circuit Short to Ground
DTC B1544 04: Mirror Motors Common Circuit Open Circuit
DTC B1600 01: Mirror Motor 1 (vertical) Circuit Short to Voltage
DTC B1600 02: Mirror Motor 1 (vertical) Circuit Short to Ground
DTC B1600 04: Mirror Motor 1 (vertical) Circuit Open Circuit
DTC B1605 01: Mirror Motor 2 (horizontal) Circuit Short to Voltage
DTC B1605 02: Mirror Motor 2 (horizontal) Circuit Short to Ground
DTC B1605 04: Mirror Motor 2 (horizontal) Circuit Open Circuit .

Probably the switch I have seen many stop working and maybe one mirror stop out of hundreds

Check fuses!

probably needs a new switch.

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 !

First, check all fuses to make sure that none are blown.

If the door lock switch works on the passenger side, then the drivers side door lock switch is probably faulty. Use a multi-meter to test the Drivers Side Door Lock Switch (Black and Pink/Light Green wires unlock the vehicle, and the Black and Pink/Yellow wires lock the vehicle)
If the switch is tested and found to be operating properly, you may have a faulty Body Security Module or Drivers Side Door Lock Actuator.

If neither of your Power Mirrors are working, you probably have a faulty Exterior Rear View Mirror Switch, Power Mirror Module, or blown Central Junction Box Fuse.

If none of your Power Windows are working, you probably have a faulty Accessory Delay Relay or a blown fuse in your Central Junction Box or a faulty Master Window Adjust Switch (all of the Power Window Switches feed through this Master Window Switch). If the Power Windows didn't stop working at the same time, you may have faulty Window Adjust Switches, or faulty Power Window Motors, this is very unlikely though. It would also be a good idea to inspect the wiring for any obvious damage.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

2003 GMC Yukon - My power mirrors stopped working.... all fuses have been checked and they are all good. Any ideas? These are the power folding mirrors. The function that allows you to fold them in for car washes etc still works.... they just will not adjust when you change drivers, or when you try to adjust them with the controls. Any ideas would be appreciated!

sound like a possible short or loose connector in the power bezel. you need to pop it off and check the connection

the fuse for the mirrors is in the fuse block inside the car on the left side of the dash-however the mirrors do not fold in with the switch,you fold them in with your hand-usually for storage(car cover)