Passenger side rear door lock would only unlock intermittently?

FIDDLENFIXIT52

MEMBER
2012 HYUNDAI I20
1.2L
4 CYL
2WD
MANUAL
75,000 MILES

To begin with the Passenger side rear door lock would only unlock intermittently. I replaced it with a second hand one, said to be good. This worked for a few days then started to be the same. Now the front passenger side door has stopped unlocking. I think the problem may be with the wiring and I think I will need to check all the cables and connections. I request the location of the BCM and also a wiring diagram for this model. Registration number EX12CHC.

9 Replies

KEN L

MASTER CERTIFIED MECHANIC
42,960 POSTS

It sounds like the BCM is going out but to be sure we should do a CAN scan. 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 the location of the BCM so you can swap it out, you can get a preprogrammed unit by searching Google or Ebay. Also, I have included the door lock wiring diagrams so you can see how the locking system works. Check out the images (below). Please let us know what happens.

Images (Click to make bigger)

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Friday, September 8th, 2023 AT 3:22 PM

FIDDLENFIXIT52

MEMBER
5 POSTS

On this UK spec i20 deadlocks are fitted, I've attached a picture from the owner's manual.
Most of the wiring diagrams you supplied are the same, but my locks have extra wiring for a 2nd motor inside the locks that deadlocks the doors unfortunately on my car this has failed locked and will not open.
On Monday I'm going to force off the door panel and then probably have to smash the lock casing to the manually open the lock.
I'll let you know how it goes.

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Saturday, September 9th, 2023 AT 2:31 AM

KEN L

MASTER CERTIFIED MECHANIC
42,960 POSTS

Wow, okay I see what you are says, they are kind of like child locks over here. I don't have access to any other wiring diagrams, so let me contact my Euro expert to see what he says.

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Monday, September 11th, 2023 AT 10:40 AM

FIDDLENFIXIT52

MEMBER
5 POSTS

Hi, I have bought a replacement lock that luckily came with the wiring multi plug (cut from the loom by the breakers).
This enabled me to test it and find the deadlock motor.
I have now managed to unlock all doors.
Replace the faulty locks.
Cut the power cable to each deadlock.
It now is all working fine.
No deadlocks as these are totally unnecessary.
Your wiring diagram is correct for the lock/unlock function.
Many thanks for all your help.

For anyone else who has this problem the deadlock power wire is blue so that it can be cut. I used a 12v battery to feed to the blue + and brown as - to force the deadlock motor to enable the unlock.
Cheers, Dave.

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Monday, September 11th, 2023 AT 2:20 PM

KEN L