1999 Ford Taurus Door Lock Problem

System has a Generic Electronic Module (GEM) which has self diagnostic functions and New Generation Star (NGS) tester can retrieve trouble codes if any are stored. These are B codes and only appropriate scan tool would be able to retrieve the trouble codes.

Checking for trouble codes would help in understand the problem and possible causes. I would suggest getting a scan done first.

The chances of all 4 actuators failing at the same time can be considered as a one in a million chances and would be hard to believe.

Test all other actuator by applying battery voltage and if all are found to be faulty, I don't believe anybody can answer your question of how and why it occurred thus.

Try the following to see if you can come up with anything.

TEST G: ALL DOORS WILL NOT UNLOCK FROM INTERIOR DOOR LOCK SWITCHES OR DOOR LOCK CYLINDER SWITCHES

1. Press driver's power door lock switch to LOCK position. If doors lock, go to next step. If doors do not lock, go to step 5.

2. Remove all door lock relay. Relay is located behind instrument panel, to right of steering column. See Fig. 1. Measure resistance in Black wire between ground and terminal No. 87A at all door lock relay harness connector. See Fig. 11. If resistance is 5 ohms or less, go
to next step. If resistance is greater than 5 ohms repair open in Black wire between terminal No. 87A at all door lock relay harness connector C255 see Fig. 15 and ground G201 (located at left kick panel).

3. Remove all door unlock relay. Press driver's power door lock switch to UNLOCK position. Measure resistance in Pink/Light Green wire between ground and terminal No. 85 all door unlock relay harness connector C256. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in Pink/Light Green wire between terminal No. 3 at driver's power door lock switch harness connector C510, splice S200 (located at left kick panel) and terminal No. 85 at all door unlock relay harness connector C256.

4. Measure voltage in Black/White wire between ground and terminal No. 87 at all door unlock relay harness connector C256. If battery voltage exists, replace all door unlock relay. If battery voltage does not exist, repair open in Black/White wire between No. 4 (30-amp fuse) at Battery Junction Box (BJB), splice S204 (located to right of all door unlock relay) and terminal No. 87 at all door unlock relay harness connector C256.

5. Remove all door lock relay. Relay is located behind instrument panel, right of steering column. See Fig. 1. Measure voltage in Black/White wire between ground and terminal No. 86 at all door lock relay harness connector C255. See Fig. 11. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Black/White wire between No. 4 (30-amp fuse) at Battery Junction Box (BJB), splice S204 (located to right of all door unlock relay) and terminal No. 86 at all door lock relay harness connector C255.

6. Measure resistance in Pink/Yellow wire between ground and terminal No. 85 at all door lock relay harness connector C255. Press driver's power door lock switch to LOCK position. If resistance is 5 ohms or less, replace all door lock relay. If resistance is greater than 5 ohms, repair open in Pink/Yellow wire between terminal No. 85 at all door lock relay harness connector C255 splice S201 (located at left kick panel) and terminal No. 6 at left master door lock switch harness connector C510.

That is possible. It could also be due to the actuators are failing and when the control gets stuck, they failed together.