Although I don't remember the details of removing the lock, I did remove the lock from the wife's 86 745T for the same problem some six years ago.

Power locks fail for three reasons in my experience: 1. The locking motor fails. The trunk lock motor in the son's 87 744T quit working. I removed the lock motor and found one of the motor leads broken off of the motor. I soldered it back on and it has worked perfectly for two years. 2. The locking relay begins to fail and does not energize the locking motors for a long enough time period to lock or unlock them. The wife's 1986 845T did this, and a used relay fixed the problem two years ago. 3. Adjustment of the locking switch in the driver's door. The 1987 and earlier model years are more prone to this than the 1988 and later model years which have an improved switch.

The locking motors are just little two lead DC motors. The locking relay energizes the motors for about one second for lock/unlock. The polarity is reversed to go from lock to unlock. To test the locking motors, you can remove the relay and jumper the electrical connectors in the realy base. The wires to the locking motors are blue/red and red/white. They are connected to the two center electrical connectors in the relay base, numbers 7 and 5. To test the locking motors, ground one electrical connector, and then energize the other for about one second. The locks will unlock or unlock if the wiring and lock motors are good. If the locking motors work on way, they will work the other way because you are simply reversing the polarity to a permanent magnet DC motor. (Starter motors don't work this way because they have field windings, and reversing the polarity reverses both the field and armature.) If you find the locks work with this test, the problem is most likely in the Central Locking Relay, but can be in the adjustment of the switch in the driver's door. The door switch on your 1988 car works by grounding one of two coils in the Central Locking Relay. You can also test by grounding the yellow/black (lock), or the green/black wires.