Car model: Toyota UZJ100 RHD. (Watch out, right hand drive versions make an absolutely nightmare to reach and replace some of its most essential relays).
The central door lock relay fails in this car. You can hear the click but it doesn't lock doors. It only works fine when the weather gets cold.
Door unlocking (unlock relay) works fine. There are 2 relays one for locking and another one to unlock doors. It is only the locking relay that gives problems.
I tested first all the door lock actuators to make sure they work fine.
I also checked wire continuity from the junction-box to the door lock actuators. Door lock wires are fine.
I tested door lock wires at the junction-box with a 12V tester. Door lock wires get power when relay works fine (doors are locked fine) but wires get no power when it fails to connect. You can hear a relay click but no power sent to the actuators.
The relay energizes or activates itself when it gets an earth signal from the Body control ECU. I had a chance to test a second Body-ECU I have. The second ECU showed the same relay behaviour (you hear the click but no power).
Thus, the conclusion was clear. I need to replace the door lock relay. Easy.
Well not so easy. This car is my father's Toyota UZJ100 RHD (right hand drive). The relay is located in the hidden side of the junction-box under the glove box. To reach this relay in the right hand drive version is an absolute nightmare. You must detach the junction box but there is no space as it is mostly hidden by the A/C pump. Thus, if you wanted to reach that relay you would have to remove the whole dashboard (Toyota also confirmed this). Crazy design.
Plan B:
Since I have the wiring diagrams of this car I thought it would be possible to identify the wires involved in the door locking circuit, disable the old relay (unplugging the ECU ground signal will disable it) and fit a new relay that could do that job.
I've never done such a fix (hack) around a junction box wiring. Any good advice from experienced guys is welcome.
What would be your preferred fix or solution if you were in my situation?
Thanks in advance.
Image A is a simplified diagram explaining how the central door lock works in this car:
Image-A-DOOR-LOCK - https://ibb.co/DQ3hcTP
Image B is the EWD of the door lock/unlock relays at the junction box:
Image-B-JUNCTION-BOX-EWD - https://ibb.co/VWrQr8b
Image C is an image of the Junction box and the wires I would have to connect to the new relay:
Image-C-JUNCTION-BOX-COWL - https://ibb.co/zPXgDV3
Image D is a picture I took from the Junction Box wires:
Image-C-JUNCTION-BOX-WIRING - https://ibb.co/9t71cWv
As I said earlier I think it may be possible to fit a new relay to fix this problem.
Does this approach make sense to you? what is the proper way to connect to those wires at the junction box (standard faston terminals? Wire gauge needed? I calculated 14 AWG to be sure. What is your advice?
Thank you in advance.
The central door lock relay fails in this car. You can hear the click but it doesn't lock doors. It only works fine when the weather gets cold.
Door unlocking (unlock relay) works fine. There are 2 relays one for locking and another one to unlock doors. It is only the locking relay that gives problems.
I tested first all the door lock actuators to make sure they work fine.
I also checked wire continuity from the junction-box to the door lock actuators. Door lock wires are fine.
I tested door lock wires at the junction-box with a 12V tester. Door lock wires get power when relay works fine (doors are locked fine) but wires get no power when it fails to connect. You can hear a relay click but no power sent to the actuators.
The relay energizes or activates itself when it gets an earth signal from the Body control ECU. I had a chance to test a second Body-ECU I have. The second ECU showed the same relay behaviour (you hear the click but no power).
Thus, the conclusion was clear. I need to replace the door lock relay. Easy.
Well not so easy. This car is my father's Toyota UZJ100 RHD (right hand drive). The relay is located in the hidden side of the junction-box under the glove box. To reach this relay in the right hand drive version is an absolute nightmare. You must detach the junction box but there is no space as it is mostly hidden by the A/C pump. Thus, if you wanted to reach that relay you would have to remove the whole dashboard (Toyota also confirmed this). Crazy design.
Plan B:
Since I have the wiring diagrams of this car I thought it would be possible to identify the wires involved in the door locking circuit, disable the old relay (unplugging the ECU ground signal will disable it) and fit a new relay that could do that job.
I've never done such a fix (hack) around a junction box wiring. Any good advice from experienced guys is welcome.
What would be your preferred fix or solution if you were in my situation?
Thanks in advance.
Image A is a simplified diagram explaining how the central door lock works in this car:
Image-A-DOOR-LOCK - https://ibb.co/DQ3hcTP
Image B is the EWD of the door lock/unlock relays at the junction box:
Image-B-JUNCTION-BOX-EWD - https://ibb.co/VWrQr8b
Image C is an image of the Junction box and the wires I would have to connect to the new relay:
Image-C-JUNCTION-BOX-COWL - https://ibb.co/zPXgDV3
Image D is a picture I took from the Junction Box wires:
Image-C-JUNCTION-BOX-WIRING - https://ibb.co/9t71cWv
As I said earlier I think it may be possible to fit a new relay to fix this problem.
Does this approach make sense to you? what is the proper way to connect to those wires at the junction box (standard faston terminals? Wire gauge needed? I calculated 14 AWG to be sure. What is your advice?
Thank you in advance.
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