2002 chevy Blazer 2 door. Power locks,and liftgate stop working.The locks will engage when I shift to drive and will disengage when placed in park. Where do I start?

Shift Lock Release
This vehicle is equipped with a shift lock release system.
If your vehicle has a dead battery and you need to
have your vehicle towed, there is a shift lock release
lever that will allow you to move the shift lever out
of PARK (P).
To access the shift lock release lever, do the following:
1. Press on the sides of the boot around the shift lever
to release the boot.
2. Lift up the boot on the shift lever and you will see an
orange lever.
3. Press the orange lever down and move the shift lever
out of PARK (P).
4. Snap the shift lever boot back in place.

Lock an unlock by them selves ? Door locks are computer controlled ,by the BCM - body control module .
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Power Door Locks Circuit Description
The power door lock system includes the following components:
• The door lock actuators
• A door lock relay
• An door unlock relay
• A driver door unlock relay
• The door lock and side window switches
• The body control module (BCM)
• The endgate lock cylinder switch /liftgate lock cylinder switch (utility)
• The keyless entry, if equipped
The door lock and liftgate mechanisms may be controlled by the following switches:
• The door lock and side window switches
• The BCM
• The endgate lock cylinder switch / liftgate lock cylinder switch (utility)
• The keyless entry, if equipped
The following locking functions are included on the vehicle:
• All the doors unlock -- All the doors will unlock, including the endgate/liftgate, when any power door unlock switch is detected. The passenger doors lock directly by pressing the lock switches. The driver door unlocks by the BCM using a driver door unlock relay.
• All the doors lock -- All the doors will lock, including the endgate/liftgate, when any power door lock switch is activated. All the lock actuators will activate directly from the power door lock switch (external to the BCM).
• The end/lift gate lock switch -- All the doors will lock or unlock from the end/lift gate lock switch.
• The lockout prevention -- This function will prevent the doors from automatically locking if the keys have been left in the ignition and the power door lock switch is operated.
The motor is protected by a built-in electronic circuit breaker (ECB). If the motor is overloaded or voltage is applied for an excessive amount of time, the ECB internal resistance increases, essentially creating an open circuit. The resistance returns to normal only after voltage is removed from the circuit, thereby restoring circuit continuity.

You have a bad switch input to the BCM !
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Try disengaging the "Auto Lock" feature in the Driver Information System when shifting in/out of Park and at a certain MPH. If that keeps it from doing it, you know the BCM Body Control Module is controlling the action. It could be it "thinks" it's unlocked when it not. May need to replace the power lock assembly. You could also try taking the battery cables off to reset the PCM/BCM. That may fix it too. Worst case, it is the BCM, and they are not cheap. Good Luck!

The power windows an power locks are controlled by a module , DDM - driver door module . As far as the locks locking when you put the vehicle into reverse an unlocking when you put the vehicle into park , that's how there are suppose to work , automatic lock an unlock feature . When you put the vehicle into any gear from park the locks should lock . Did she hit window lockout function ?

The power door lock system consists of the following components:
• The driver door module (DDM)
• The passenger door module (PDM)
• The body control module (BCM)
• The driver information center (DIC)
• The rear door lock switch
• The door lock relay
• The door unlock relay
• The liftgate lock relay--utility vehicles with liftgate only
• The reversible door lock actuators in each of the doors and liftgate
• LOCKS 20A fuse (rear lock/unlock relay supply voltage)
• ECC 10A fuse (liftgate lock relay supply voltage .

Programmable Automatic Door Locks
The automatic door lock feature can be programmed to control the door lock system. The automatic door lock feature is factory programmed to have all doors lock and unlock. For detailed instructions on programming the automatic door locks, refer to Vehicle Personalization in Personalization.
When the automatic door lock feature is programmed to control the door lock system, the driver door module (DDM), passenger door module (PDM) and body control module (BCM) will lock the vehicle doors if the following inputs are true:
• Ignition 1 input is active.
• All door jamb switch inputs are inactive.
• Cargo door or liftgate/liftglass ajar inputs are inactive.
• Transmission is shifted out of park.
This automatic door lock function will only occur once per ignition cycle unless, a door jamb switch input changes state to active and back to inactive. Then the DDM, PDM and BCM will lock all doors again.
Once the automatic door lock feature has locked the doors, the BCM will then unlock all the doors when the transmission is shifted into park.
Driver, Passenger and Cargo Door Lock System Operation
The front power door lock switches are integral components of the driver door module (DDM) and passenger door module (PDM). The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The rear door lock switch provides a lock and unlock signal to the body control module (BCM). The BCM upon receipt of a lock or unlock signal will control the rear door lock relays and also send a Class 2 message to the DDM and PDM to perform the appropriate function.
The modules which activate the power lock motors are:
• The DDM (driver door lock actuator).
• The PDM (passenger front door lock actuator).
• The BCM (both rear door lock actuators and cargo door/liftgate).
The DDM and PDM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.
The rear passenger and cargo doors differ slightly in that they use lock and unlock relays. The relays supply and coil sides receive a constant voltage through the battery voltage supply circuit. The normally closed contacts are connected to ground and the control side is connected to the BCM. Once a door lock or unlock request has been received by the BCM, the BCM will ground the control side of the appropriate relay. This energizes the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.

driving in 4wd on hard surfaces produces what is known as torque wind up as the wheels cannot slip so the variations of distance going around corners , dips in the road etc place considerable strain on the transmission , transfer case , drive lines and diffs
that is why it is difficult to get out of 4wd unless you drive with 2 wheels on a grass verge to relieve that torque wind up
as for the noise check wheel bearings and the cv ("U") joint at that wheel as there appears a proble where the dog teeth in the hub are not engaging properly or are jumping out of engagement

Take the liftgate inside panel off an check the wiring , connections etc....
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The liftgate will lock any time the vehicle is shifted out of park on vehicles equipped with an automatic transmission and at vehicle speeds exceeding 5 kph with manual transmission. This happens in conjunction with auto door locks if enabled or independently of auto door locks if the feature is disabled. This ensures that the liftgate is locked anytime the vehicle is shifted out of park or when the vehicle is in motion.
The liftgate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a liftgate lock function has been received by the BCM. The BCM will then ground the control side of the liftgate lock relay. This energizes the relay and allows voltage to be applied to the liftgate lock actuator lock control circuit. Since the other side of the liftgate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the liftgate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and liftgate will unlock.
The BCM also runs diagnostics on the liftgate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the liftgate lock circuit and that the liftgate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following

Power Door Locks Inoperative - Endgate/Liftgate

Schematic Reference: Door Lock/Indicator Schematics
Connector End View Reference: Power Door Systems Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Activate the door lock switches to the lock and unlock positions.
Do both rear passenger doors lock and unlock?
YES - Go to Step 3
NO - Go to Power Door Locks Inoperative
3
Did the liftgate lock actuator lock and unlock?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 4
4
Disconnect liftgate door lock actuator.
With a test lamp connected to a good ground, probe the door lock actuator lock circuit at the door lock actuator harness connector.
Activate a door lock switch to lock position.
Does the test lamp illuminate?
YES - Go to Step 5
NO - Go to Step 7
5
With a test lamp connected to a good ground, probe the door lock actuator unlock circuit at the door lock actuator harness connector.
Activate a door lock switch to unlock position.
Does the test lamp illuminate?
YES - Go to Step 6
NO - Go to Step 8
6
Inspect for poor connections at the harness connector of the door lock actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 10
NO .. Go to Step 9
7
Repair the open door lock actuator lock circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 10
--
8
Repair the open in the door lock actuator unlock circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 10
--
9
Replace the liftgate door lock actuator. Refer to Door Lock Actuator Replacement in Body Rear End.
Did you complete the repair?
Go to Step 10
--
10
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2

There is a vacuum actuator mounted on the front differential that locks the shafts to engage four wheel drive.

The 2006 Vibe no longer has that feature. It was discontinued after 2005. I have the 2005 so I know how to change it. If your 2006 is able to change then here are the directions from my 2005.
Programmable Automatic
Door Locks
If you have an automatic transaxle, your vehicle is equipped with an auto door lock/unlock feature which enables you to program your power door locks.
Your vehicle left the factory programmed to Mode 4.
The following is a list of the available programming options:
Mode 1: All doors and liftgate lock when the shift lever is moved out of PARK (P) with the ignition on and all doors and liftgate closed. There is no automatic door unlocking.
Mode 2: No automatic door locking or unlocking.
Mode 3: All doors and liftgate lock when the shift lever is moved out of PARK (P) with the ignition on and all doors and liftgate closed. All doors and liftgate unlock when the shift lever is moved to PARK (P) with the ignition on.
Mode 4: All doors and liftgate lock when the shift lever is moved out of PARK (P) with the ignition on and all doors and liftgate closed. All doors and liftgate unlock when the ignition switch is turned from ON to ACC or to LOCK.
To change the mode you are in, do the following:
1. Set the interior lamp control dial to the door position.
See Interior Lamps Control on page 3-16.
2. Move the shift lever into PARK (P) and close all doors and liftgate.
3. Turn the ignition to ON.
4. Within five seconds after the ignition is turned to ON, press and hold the power door lock switch in
the lock position for about five seconds.
5. The interior lamp will flash to indicate that the mode has been changed. For example, if the lamp flashes once, the function has been changed to Mode 1.
If the battery is disconnected or run down, the mode is changed to the initial mode which is Mode 4.

I now these trucks pretty well, I own 2, a 2000 two door and a 95 4 door and before them I owned a 88 and an 87, so look I suggest you use 4 hi but in low geer(1st geer) and just let it grab by itself, cause I find first thing it's hard getting into 4 low cause you must be in neutral,and I usually engage it with only the ignition on without actually running the truck to make sure it actually engages, we get a lot of snow up here so I'm letting experience speak for itself, hope it helps...

goodluck...

1- STOP THE VEHICLE
2- MAKE SURE IS IN NEUTRAL POSITION
3- ACTIVATE 4WD (HIGH) MODE( MANUAL OR ELECTRONIC SWITCH SELECTOR
4- MOVE LEVER SHIFT TO ''D' DRIVE POSITION
IF THIS DOES NOT RESOLVE CHECK TRANSFER CASE SWITCH