I am having an issue with my 1999 F350 power door locks when using the remote key fob. Years ago I replaced the stock actuators with aftermarket "bayonet" units and have been working fine until last week, I found the rear locks didn't work, then the passenger door lock quit and then they all stopped working, all within about an hour. I checked wiring, voltages at switches and replaced 2 relays under the dash in hopes of fixing the issue, but still no door lock movements. After removing the factory wire leads to the driver's door actuator, I found it was dead and did so on the other 3, same diagnosis. Couldn't believe all 4 failed at one time within a couple hours, but the evidence was plain to see. After installing new actuators and using the door lock switches, everything worked, or so I thought. I am having an issue with using the remote to lock the door actuators, using the remote will unlock them just fine. Pressing the lock button on the remote once doesn't lock the doors and pressing it twice makes the horn sound but still no actuator movement. I can hear a very slight click under the dash upon door lock attempt with remote, not as load a click as before replacing relay. I will replace both relays again to see if I installed a bad one. That said, could this condition I am experiencing be a GEM issue? I looked for water/moisture intrusion but found no evidence of any. I seem to have no other electrical issues with wipers, power windows and etc, and the power door locks do work correctly when using the door switches. Please advice and thank you in advance for any and all assistance will be much appreciated.

 

IIRC, the front passenger door is the master for the wiring. When I replaced mine I found a weak connection to ground just inside the right kick panel. They have been working fine since. That was back in 2016.
I agree tho, not likely all failed at the same time.

 

Thank you for your reply. I checked all fuses and relays in both fuse boxes and/or replaced all the relays under the dash with known good units, the 4 over the trans tunnel then the 3 on the lower left hand side of the radio(turn signal/hazard was one of them) and still no change. I also substituted the driver's side power window/door lock panel to check that the power door lock switch wasn't the culprit-no change. I did check all the actuators and in deed all were dead. I'm thinking the GEM unit was continually sending a signal to lock the doors and that caused the motors to burn out and possibly the door lock output trigger from the GEM module to quit working. I will remove the under dash fuse panel/GEM module and check for output from the GEM's power door lock port/wire when using the remote. I will post my findings. Thanks again for the reply.

 

After removing both positive battery terminals, I removed the under-dash fuse panel with GEM unit attached and let hang under the dash, I reattached DS battery's positive terminal for testing. Once I found which port/wire color was used for door lock pulse output on the GEM wiring harness plug and using my VOM to see if I had any voltage reading differences when I pressed remote's lock button, no reading differences were noticed. I then unplugged the GEM plug that had the lock wire(Pink/Yellow) and used a piece of stiff wire placed into the back of the plug where the P/Y wire resides and then placed a ground signal on it to check door lock relays/wiring, the doors locked correctly. I did remove the GEM unit and opened it up to see if there was anything obvious as to why lock feature didn't work, everything looked good/no damage. Looks like the GEM module is the culprit. Ordered one and hope to install it over the weekend.

 

Someone correct me if I'm wrong, but didn't the 99's have an issue with the seal on the windshield leaking causing water to drip on the GEM which caused issues such as this ?

 

Installed another GEM module today, once remotes programmed, now everything finally works as it should.