Strange lock key problem?

1996 DODGE GRAND CARAVAN
125,000 MILES • 3.3L • 6 CYL • 2WD • AUTOMATIC
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DANIBOY46
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I have had from new. Low 125,000 miles now. It has been a trouble-free vehicle with one weird exception. Even the dealer gave up: First of all, both my key fobs work normally. Door lock switches inside work normally. Vehicle doors correctly lock automatically at 15MPH. But, if I try to unlock the vehicle using a key in any of the three key locks (driver door, passenger door or tailgate) the following happens: the door(s) unlock but within a split second, with key still in the lock, the key in my hand is forced back by the actuator leaving all doors locked. If I then try to unlock several times then one time, I will get lucky, and door(s) stay unlocked, and key can be pulled out normally. It has been this way since just after the warranty expired. Obviously, it cannot be an actuator problem with all three actuators developing the same fault while the vehicle was basically new. I have never heard of anyone else with this problem. What on earth is causing it? Is there some faulty timer at work here, or a bad relay?
Aug 29, 2023 at 8:37 AM
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STRAILER
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It sounds like the BCM is going out or you have a loose connection to ground, here is the system wiring diagrams so you can see how the system works and which wires to check for ground. This guide can help you test the connections. Also, we should do a CAN scan which can help tell us if this is the problem as well. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:


https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is how to change out the BCM, you can get a preprogrammed unit by searching Google or Ebay. Check out the images (below). Please let us know what happens.
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Aug 29, 2023 at 5:03 PM
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DANIBOY46
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Thank you for the info. I cannot go purchasing that expensive test equipment or removing the BCM. I'll probably risk more damage doing the latter. However, I focused on the lock relays in the diagrams you sent as they are in the junction block attached to the BCM. I reseated the driver door relay E and bingo the driver door key problem went away - so far. Passenger and tailgate still have the problem. I haven't tried reseating the other two door lock relays A and B yet, but hope reseating them will resolve the passenger and tailgate key prob.
Sep 1, 2023 at 10:06 AM
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STRAILER
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Nice work, connections problems can be fixed this way, but be on the lookout for a bad relay as well. Let me know what happens after the other relays are re-seated.
Sep 2, 2023 at 10:02 AM
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DANIBOY46
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Hi Ken
I reseated the other two "lock relays" (A & B) in the junction block today and again -Bingo! The passenger door and tailgate locks no longer "forcibly bounce back" when the key is used. The key now unlocks and locks the three key locks normally. After all these years I finally have my three key locks back to normal. What a sad situation that the dealer could not figure out the problem so long ago. Perhaps this relay "tip" will help others at no cost should they encounter this problem.
If it helps others with (96 and probably 97-2000 Caravans): Relays A and B are the two relays on the left in the top row. Relay E (driver door) is the relay on the left in the next row down.
Sep 5, 2023 at 6:00 PM
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STRAILER
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Nice work finding the problem and thanks for letting us know. Please use 2CarPros anytime we are here to help.
Sep 6, 2023 at 10:05 AM