The motor for the lumbar support for the back of the driver's seat operates in only one direction. In the back of the seat, you can hear a very soft click when you release the switch, but the adjusting mechanism will not move. It only moves outward, toward your back. I cannot get the seat back to flatten out.

unplug it or pull fuse

Your best bet , have it checked for DTC'S - diagnostic trouble codes first ! Electronic control modules involved ! Can't check with a OBD 2 code reader , need advanced scan tool . No codes , check B+ voltage and ground to the module .
Power Seat Inoperative (With Memory A45)
Memory Seat Feature Inoperative
Circuit/System Description
Battery voltage is supplied at all times to the memory seat module (MSM) from the MDL-MEM 10A fuse located in the rear fuse block. This voltage is used by the MSM for logic power and to supply battery reference voltage to the seat and lumbar adjuster switches. Battery positive voltage is also supplied at all times to the MSM from the PWR SEAT 25A circuit breaker. This voltage is connected to a power rail internal to the MSM and is used to drive the power seat motors, lumbar motors, and seat heater elements on vehicles equipped with heated seats. Each seat and lumbar adjuster motor is controlled by the MSM through 2 motor control circuits. The MSM connects all motor control circuits on the power rail to a common reference point whenever they are not in operation. This reference point is biased to approximately 2.5 volts. The MSM checks to see if the reference voltage is shorted to ground or battery before enabling any of the seat or lumbar motors.

Circuit/System Description
Reference voltage is supplied to the memory switch from the driver door module (DDM). When a memory switch is pressed, reference voltage is applied through the switch contacts, a series of resistors and thorough the memory switch signal circuit to the DDM. The door module then sends a serial data message to the memory seat module (MSM) indicating the memory recall request. The MSM then commands the appropriate seat motors to move to the pre-recorded seat positions stored in memory in response to the switch input.

lumbar on the driver seat Shawn, Its cable driven plastic plate. It can possibly be repaired once you disassemble it and can see it, if not repairable you can replace the lumbar. Check the attached links,forums with instruction and guides, Good luck
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Thread Town Car Lumbar motor assembly replacement

Power seat lumbar support repairs

Drivers Power Seat Just Stopped Working Lincolns OnLine Message Forum

The control module for that system is under the drivers seat. Make sure the door switches are applying power to the motor.

You don't mention what year your Yukon is ? This could very well be a control Module problem .
I'll post how the power memory seat's work or are suppose to work !

Memory Seats Description and Operation

Battery voltage is supplied to the memory seat module through a 25 A circuit breaker. The memory seat module supplies the seat adjuster switch assembly with a battery positive reference voltage. While the seat adjuster switches are in an inactive state the switch contacts are closed to the adjuster switch common circuit. When a seat adjuster switch is pressed to an active state the switch contact is closed to the reference voltage circuit. Battery voltage on a switch signal circuit indicates to the memory seat module the switch status is active. Each seat adjuster motor is controlled by the memory seat module through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the memory seat module. The memory seat module operates the seat adjuster motors by switching one of a motors control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.


Memory Set/Recall Operation
The seat adjuster motors are equipped with internal position sensors. The adjuster motor position sensors are monitored by the memory seat module and are used to determine the seat position when storing or recalling memory settings. The driver seat adjuster motors use potentiometer type position sensors. The position sensors are supplied with a 5 V reference and ground circuits from the memory seat module. The position sensor signal circuits return to an analog input within the memory seat module. During adjuster motor operation the position sensor provides a voltage change proportional to the change in revolution of the adjuster motor shaft. The memory seat module monitors the voltage from the position sensor signal circuits to determine the adjuster motor positions when storing or recalling memory seat position settings.
The memory recall switch assembly on the driver door provides inputs to the driver door lock/window switch. Battery voltage is supplied to the memory recall switch assembly from the driver door lock/window switch. When a RCL 1, RCL 2, or EXIT switch is pressed, the switch contacts close the appropriate switch signal circuit to the battery voltage supply circuit within the memory recall switch assembly. When the driver door lock/window switch receives active switch signals from the memory recall switch assembly, the appropriate commands are sent to the memory seat module using the GMLAN Serial Data circuit. The Body Control Module software version determines the personalization features available.
Memory seat recall operation is allowed only with the transmission selector lever in the PARK position while the ignition is on. The transmission selector lever position data is provided to the memory seat module by a message through the GMLAN Serial Data circuit.

There are somethings listed you are not familiar with , like GMLAN Serial Data circuit ,maybe Body Control Module software etc... GMLAN is a communincation network that the computers on the vehicle uses to share information , transmit commons etc... you can google it to read about it .

There are DTC'S - diagnostic trouble codes that can set in the module in control . Do you know what DTC'S are .

DTC Descriptors
DTC B1825 01: Driver Seat Recline Position Sensor Circuit Short to Battery
DTC B1825 06: Driver Seat Recline Position Sensor Circuit Short to Ground or Open
DTC B1825 5A: Driver Seat Recline Position Sensor Circuit Plausibility Failure
DTC B1850 01: Driver Seat Lumbar Horizontal Position Sensor Circuit Short to Battery
DTC B1850 06: Driver Seat Lumbar Horizontal Position Sensor Circuit Short to Ground or Open
DTC B1850 5A: Driver Seat Lumbar Horizontal Position Sensor Circuit Plausibility Failure
DTC B1860 01: Driver Seat Lumbar Vertical Position Sensor Circuit Short to Battery
DTC B1860 06: Driver Seat Lumbar Vertical Position Sensor Circuit Short to Ground or Open
DTC B1860 5A: Driver Seat Lumbar Vertical Position Sensor Circuit Plausibility Failure
DTC B2355 01: Driver Seat Front Vertical Position Sensor Circuit Short to Battery
DTC B2355 06: Driver Seat Front Vertical Position Sensor Circuit Short to Ground or Open
DTC B2355 5A: Driver Seat Front Vertical Position Sensor Circuit Plausibility Failure
DTC B2365 01: Driver Seat Rear Vertical Position Sensor Circuit Short to Battery
DTC B2365 06: Driver Seat Rear Vertical Position Sensor Circuit Short to Ground or Open
DTC B2365 5A: Driver Seat Rear Vertical Position Sensor Circuit Plausibility Failure
DTC B2375 01: Driver Seat Assembly Horizontal Position Sensor Circuit Short to Battery
DTC B2375 06: Driver Seat Assembly Horizontal Position Sensor Circuit Short to Ground or Open
DTC B2375 5A: Driver Seat Assembly Horizontal Position Sensor Circuit Plausibility Failure

5) Memory Seat Module is under the front of the driver seat , you could look under an see if all the connectors are fully seated.

The best diagnostic step would be to hook up the factory scan tool an see what the computer is seeing as far as inputs from the switch an outputs it's sending . I wouldn't suggest you take the seat apart an try testing electrical inputs etc.... unless you very familiar with automotive electrical systems an circuits .

The dirver seat module is attached to the underside of the seat frame. It must be calibrated if replaced. The dealer can use a tool to get failure codes (DTCs) from teh module. 1/2 hour labor charge to extract codes.


Front Seats
The front seats have the following features:

• Driver memory
• Power lumbar (optional)
• Manual lumbar
• Horizontal, vertical front and rear tilt adjustments (driver)
• Horizontal, vertical front tilt adjustment (passenger)
• Power recline
• Climate controlled (optional)

Adjustment of the seat may be accomplished with the seat control switch located on the side of the seat.
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Principles of Operation
Driver Power Seat - Memory
NOTE: The memory power seat track may stall when operating at 0°C (32°F) or below. Once the vehicle's interior temperature rises above 0°C (32°F), normal operation should return.
The driver power seat is controlled by the driver seat module (DSM). The DSM does not need to be configured, however the driver seat does need to be calibrated when the DSM is installed. The driver seat control switch provides voltage to the DSM when activated. The NEUTRAL position of each driver seat control switch position is a ground state through the seat control switch contacts. A voltage input causes the DSM to power the appropriate motor until the input is removed. Ground is the normal state of the motor circuits through the DSM and is not switched to control the motors. The DSM internally switches the appropriate line from ground to power to adjust the motors.
As the seat is adjusted, the DSM constantly monitors the motor position sensors to record the current seat position. The DSM will remove power from the motor upon termination of the seat control switch input or if the DSM does not see movement from the motor by monitoring the position sensor. The DSM must be calibrated to the seat track it is controlling. For additional information, refer to Seat Calibration. Once the DSM is calibrated to the seat track, it will only allow movement within the calibrated range.
Seat Calibration
The DSM is calibrated using a diagnostic tool. The calibration procedure automatically powers the driver power seat through its full range of motion and records the FULL STOP positions by monitoring the motor position sensors. Once the FULL STOP positions or range of the seat have been recorded, the DSM will only operate within the calibrated range. Any input attempting to drive the seat beyond the calibrated range will be ignored. This calibration is used for all seat control functions including manual switch control and memory recall positioning. During the seat calibration, the DSM may identify a function that is inoperative, such as a position sensor not changing. If the DSM identifies a concern that has a related diagnostic trouble code (DTC), the DSM will set the related DTC at the end of the validation procedure.
The calibration procedure powers the seat track adjustments to the end of their travel, which is determined by the DSM sensing a change of state in the motor position sensors. If there is a concern with the seat track or motor position sensor that limits the travel, the DSM will interpret the stopping point as the end of travel and store the position. The DSM is not able to determine if the seat has moved to its FULL TRAVEL position. It is only capable of monitoring and storing the amount of travel seen by the position sensor changing states.
For additional information on carrying out the power seat calibration procedure, refer to the diagnostic tool operating manual.
Memory Seat
Memory seat positioning can be recalled with the memory switches on the driver door panel or a programmed remote keyless entry transmitter. In either case, the DSM receives a memory recall 1 or 2 command from the driver door module (DDM) over the SCP communication network. The memory recall switches are a hardwired input to the DDM. The DDM also receives the remote keyless entry transmitter signals. Once a valid memory recall command is received from the DDM, the DSM moves the driver seat to the position stored in memory by powering the appropriate motors and monitoring the motor position sensors until the position is reached.
This system allows automatic positioning of the driver seat to 2 programmable positions.

• To program position 1, move the driver seat to the desired position using the seat control switch. Depress the set button. Within 5 seconds, depress button 1.
• To program position 2, repeat the previous procedure using the set button and button 2.
• To recall position 1, depress button 1. To recall position 2, depress button 2.

A position can only be recalled when the transmission selector is in PARK or NEUTRAL. A position may be programmed at any time.
Easy Exit/Easy Entry
The easy exit function moves the seat backwards about 2 inches when the ignition key is removed from the ignition switch. The DSM receives a key out command over the SCP communication network and powers the driver seat rearward. This function will not operate if the seat is less than the travel distance to the end of the track, or the function has been deactivated at the message center driver personality settings. The DSM will also cancel this operation if a valid input command is received, such as the seat control switch or memory recall request.
The DSM will record the current seat position before powering the seat for an easy exit function. This recorded position will be used to return the seat to this position on the easy entry operation. During easy entry operation, the seat is returned to the position previous to the easy exit operation. Easy entry operation will be cancelled if a valid input command is received by the DSM.
Passenger Power Seat
The passenger power seat motors are hardwired to the passenger seat control switch. The circuits are normally at ground through the seat control switch. The individual circuit is switched to power when the specific adjustment position is selected.
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Visual Inspection Chart Mechanical Electrical

• Front seat track motors
• Front seat track binding or obstructed
• Front seat backrest power recline
• Lumbar motor
• Climate controlled seat ducts

• Driver door module fuse(s):
  • Central junction box (CJB) fuse 7 (5A)
  • CJB fuse 22 (10A)
• Driver seat module fuse(s):
  • Battery junction box (BJB) fuse 21 (20A)
  • CJB fuse 7 (5A)
• Passenger power seat BJB fuse 28 (20A)
• Rear heated seat fuse(s):
  • BJB 11 (20A)
  • CJB fuse 16 (5A)
• Driver power lumbar BJB fuse 21 (20A)
• Passenger power lumbar BJB fuse 28 (20A)
• Driver and passenger climate controlled seat module fuse(s):
  • BJB fuse 26 (30A)
  • CJB fuse 16 (5A)
• Seat control switch
• Memory set switch
• Lumbar seat control switch
• Seat fan motor
• Climate controlled seat module
• Climate controlled seat switch

HI. There are only two causes for this particular issue. The most common will be a failed switch assembly. This should be located on the side of the drivers seat. This switch is responsible for transferring the movement commands to the actual motor/gear assembly, which is located on the rail structure under the seat in question. If your lumbar section is responding to commands, but the others fail, this will lead to a failed switch circuit. the entire switch board will need to be replaced, in this case.

Now, if you command the set to move forward, and all you hear is the motor running , but no movement, this will lead to a failed gear assembly. This will be the second cause of no forward/backwards movement. In this case, the entire motor/gear assembly will need to be replaced, due to the fact that the gears are not sold separately. The are shipped as a kit with the motor.


It is required that you order this type of replacement part directly from the dealership.

• NOTE_ I have seen in most cases that the there was jam, due to pieces of the gear assembly breaking off, and jamming up the mechanism. in order to properly inspect for damage of this nature, it will be necessary to remove the seat.

First of all, check under the seat where there should be a cluster of wires. Sometimes if the power seat is used alot by sliding back and forth, without this cluster of wires being secured, occassionally a wire can get cut.
The runners on which the seats move are metal and cut wires easily. Secondly, the plug also located under the seat could have gotten wet or accidently came unplugged from someones feet in the back or objects and debris.
Another possibilty that will keep power seats from working is the power seat motor. In most cases, this small electrical motor is located directly under the power seat control panel or very nearby
Also you could check the fuses in the fuse box, located directly above the driver's left foot area. Power seats are usually on thier own circuit which means if the power seat fuse is blown, that is the only malfunction that will be noticed, versus other circuit which have many power items on one circuit. For example dash light, clock, and temp lights don't work, one fuse will fix the problem. Power seats operate on one fuse circuit which could have one or more fuses depending on the options of your seats. E.g. heated or not, lumbar, etc.

which maxi fuse gets hot ? # fuse , plus amps The power seats uses a 30 amp circuit breaker ,not a fuse . The horn gets power from the same circuit breaker . . Sounds like something is drawing to much current. Do you know how to use a amp meter to test current flow . Disconnect componets till draw goes away ? How to use a wiring diagram to pin point areas in a circuit to test ?
Is there corrosion on the pins where the seat circuit breaker plugs into ? Reach under your seats an see if one of the seat motors is hot .
DeVille
The left and the right power seat system consist of the following components:
• The seat switches
• The seat relay modules
• The 4 reversible motors:
- The front vertical motor
- The rear vertical motor
- The horizontal motor
- The recline motor
These 4 motors operate independently of each other.
When the entire seat switch is pushed to the FORWARD position, the forward input of the of the seat relay is grounded.
The seat relay module supplies battery positive voltage (B+) with a ground to the horizontal motor, in response to this input. In order to drive the seat forward, the motor runs until the switch is released.
The BACK position works similar to the FORWARD position with the exception that the voltage polarity supplied by the seat relay module is reversed causing the motor to run in the opposite direction. This action drives the seat backward.
These recline switches operate similar but independently:

The seat relay module could be bad , If you don't know how to do automotive electrical circuit testing it mite be a good idea for you to take your vehicle to a qualified repair shop.
Could have diagnostic trouble codes stored as well .
DTC B0846 +5 Volt Reference Out of Range
DTC B0856 Battery 2 Out of Range
DTC B1656 EEPROM Write Error
DTC B1658 EEPROM Checksum Error
DTC B1982 Source/Battery Voltage High
DTC B1983 Source/Battery Voltage Low
DTC B2101 Recline Aft Switch Failed (Eldorado)
DTC B2101 Recline Aft Switch Failed (DeVille)
DTC B2102 Recline Forward Switch Failed (Eldorado)
DTC B2102 Recline Forward Switch Failed (DeVille)
DTC B2103 Rear Vertical Down Switch Failed (Eldorado)
DTC B2103 Rear Vertical Down Switch Failed (DeVille)
DTC B2104 Rear Vertical Up Switch Failed (Eldorado)
DTC B2104 Rear Vertical Up Switch Failed (DeVille)
DTC B2105 Horizontal Aft Switch Failed (Eldorado)
DTC B2105 Horizontal Aft Switch Failed (DeVille)
DTC B2106 Horizontal Forward Switch Failed (Eldorado)
DTC B2106 Horizontal Forward Switch Failed (DeVille)
DTC B2107 Front Vertical Down Switch Failed (Eldorado)
DTC B2107 Front Vertical Down Switch Failed (DeVille)
DTC B2108 Front Vertical Up Switch Failed (Eldorado)
DTC B2108 Front Vertical Up Switch Failed (DeVille)
DTC B2109 Lumbar Aft Switch Failed
DTC B2110 Lumbar Forward Switch Failed
DTC B2111 Lumbar Down Switch Failed
DTC B2112 Lumbar Up Switch Failed
DTC B2115 Recline Sensor Failed
DTC B2116 Rear Vertical Sensor Failed
DTC B2117 Horizontal Sensor Failed
DTC B2118 Front Vertical Sensor Failed
DTC B2119 Lumbar Forward/Aft Sensor Failed
DTC B2120 Lumbar Up/Down Sensor Failed
DTC 2130 Seat Motor Failure

there is a relay that controls the lumbar its under the seat unbolt seat replace the clicking relay