Remote with new battery seems to have all functions except the lock door function. The armrest control has normal function and will lock and unlock. The remote will then unlock but will not lock. This is a 1998 Ford Explorer XLT.

NO FOBS DETECTED
Refer to Keyless Entry System Description and Operation

Keyless Entry System Description and Operation - Passive
Passive keyless entry allows entry to a locked vehicle without pressing any buttons on the keyless entry transmitter. You must only have the transmitter with you. This passive system is also part of the vehicle starting system. It allows you to start and run the vehicle having only the transmitter as your key. The passive entry and starting system use low frequency antennas in 4 different areas on the vehicle to determine the location of the transmitter. When passively opening a locked door or the rear compartment lid, you must have a programmed transmitter with you in your pocket, purse, or briefcase. As a customer opens the door handle or presses rear compartment touch pad, the low frequency antenna sends out a challenge to the keyless entry transmitter. The transmitter must be in a one meter range of the door or rear compartment lid in order to receive the challenge. If the challenge is met, the transmitter will respond, allowing the door to be unlocked and opened. Passive entry allows you to operate the following features:
• Passive door unlock/unlatch
• Passive rear compartment lid release
• Illuminated entry lamps
• Vehicle starting
The keyless entry system has the following components:
• Keyless entry transmitters
• LH and RH door antennas (part of the door handle assembly)
• Rear compartment antenna
• Console passive antenna
• Console active antenna
• Instrument Panel Module (IPM)
• Rear Integration Module (RIM)
• Remote Control Door Lock Receiver (RCDLR)
• External RF Antenna (includes coax from RCDLR to back glass)

Remote Control Door Lock Receiver (RCDLR)
The RCDLR is a multi-function module which controls all the vehicles antennas for passive keyless entry functions. The RCDLR also acts as the receiver for active keyless entry and tire pressure monitoring (TPM) functions, as well as controlling all immobilizer functions.
The RCDLR's RF antenna is located in the back glass, and there is a coax cable connecting the glass antenna to the module located in the trunk.

Your best bet , take it to a qualified repair shop that has the factory Tech 2 scan tool or someother professional type scanner that can read • Rear Integration Module (RIM) DTC'S - diagnostic trouble codes .

The BCM - body control module is what controls the power lock's , disconnecting power can cause some functions to need resetting .
Have the BCM checked for DTC'S - diagnostic trouble code's , that would be my first step . Do you know what wiring diagrams are an how to read them ? Free wiring diagrams here
http://www.bbbind.com/free-tsb Enter vehicle info. Year , make , model an engine size . Under system click on body & accessories , then under subsystem click on power lock's .

Battery Disconnect or Replacement Problems


Driver Door Unlock Operation
When any of the door lock switches are placed in the unlock position, a ground signal is applied to the BCM through the door unlock signal circuit. Upon receiveing this signal, the BCM grounds the control side of the driver door unlock relay through the driver door unlock relay control circuit. Since the other side of the driver door unlock relay winding is connected to battery voltage, the relay is energized. This causes the contacts to close and complete the path from the DRV LKS fuse through the battery voltage circuit. Voltage is then applied to the unlock side of the driver door lock actuator through the driver door lock actuator unlock control circuit. Since the other side of the the driver door lock actuator is connected to the normally closed contacts of the door lock relay to ground, the driver door unlocks.
The driver door unlock function can also be accomplished by the BCM supplying ground to the driver door unlock relay control circuit by either of the following:
• A keyless entry unlock transmission
• A lock out prevention function

DTC B3130 00: All Door Unlock Circuit
DTC B3135 00: All Door Lock Circuit

Circuit/System Description
When any of the door lock switches are placed in the lock position, a ground signal is applied to the BCM through the door lock signal circuit. Upon receiving this signal, the BCM grounds the control side of the door lock relay through the door lock relay control circuit. Since the other side of the door lock relay coil is connected to battery voltage, the relay is energized. This causes the contacts to close and complete the path from the battery voltage circuit. Voltage is then applied to the lock side of the door lock actuators through the door lock actuator lock circuits. Since the other side of the all the door lock actuators are connected to the normally closed contacts of their respective unlock relays to ground, the doors lock.

The rear hatch locking is computer contolled .
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:
• An open ECC fuse
• An open or short to ground in the liftgate lock relay battery positive voltage circuit
• A faulty liftgate lock relay
• An open or short to ground in the liftgate lock relay control circuit
• A short to ground in the liftgate lock actuator lock control circuit
• A faulty BCM

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 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)

If i were to guess i would say you mite need a new lock actuator , but i don't guess . You could take the hatch inside panel off an check for B+ voltage for the lock actuation as someone pushes the switch . Or have it checked for codes .

So , the power door locks won't lock or unlock with switches inside the vehicle or with the keyless entry remote fob.??? Is this correct ????
Do you know what a BCM - body control module is ? Do you know what diagnostic trouble codes are ? If not your best bet would be to take your vehicle to a GM dealer or someother qualified repair shop.
DTC B3142 or B3143
The body control module (BCM) provides an output to the driver switch assembly through the door unlock control circuit for controlling automatic door unlock, anti-lockout, and keyless entry unlock functions.
DTC B3152 or B3153
It could be the driver door master switch , could have broken wires inside the rubber boot from the body to the door . Do the power windows work ?
The keyless entry system has the following main components:
• The transmitters
• The body control module (BCM)
When you press a button on a transmitter, the transmitter sends a signal to the BCM. The BCM interprets the signal and activates the requested function.

How did you do this ,,checked and made sure locks and remote programmed,they were,but still do not work ?????

Need a scan tool to program
Important: All key fobs must be programmed each time any one fob is programmed. The scan tool must stay connected until all of the transmitters are programmed.
Install a scan tool and navigate to the BCM Module Setup menu.
Select Program Key Fobs.
Follow the scan tool on-screen directions.
When the programming operations have completed, operate the transmitter functions to verify correct system operation.

Check to see if your central locking still works on all doors and that you can also operate the driver's door central lock motor.
This can sometimes be an issue with the door lock motors themselves and not necessarily the key.

have you tried to press/hold lock button for 30 secs.
the code changes everytime you use the remote so that only your remote unlocks your car,not everybody elses.the key has a code inbuilt into it so the car will only start with your key...(this is dealer programmable)

If you cannot lock/unlock any doors at all, change the battery on your remote. If all the other doors work, but not the driver's door, there's a malfunctioning magnetic switch on the door.

you have a bad relay.. the 'lock' relay.

Emergency operation of rear lid
If the rear lid cannot be opened with the radio
remote control (e.g., if the battery of the remote
control is dead), the emergency operation must
be performed:
1. Unlock and open the driver's door with the
vehicle key.
2. Switch on the ignition so that the alarm system
will not be triggered.
3. Check if the TAILGATE function is activated in
the multi-purpose display of the instrument
panel.
Please observe the chapter “TAILGATE” on
Page 119.
4. Press the central locking button in the armrest.
The rear lid is now unlocked and can be opened
with the unlocking handle

It may be failing contacts in your remote; these are normally little carbon buttons that can either get fouled with contaminents or wear out if made too thin.
You may have to replace the remote to regain normal function.