horschi
Automotive
- Feb 16, 2021
- 5
Car model: Toyota UZJ100 RHD. (right hand drive version makes 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 it click but it doesn't lock doors. It only works fine when the weather gets cold.
Door unlocking (unlock relay) works fine. It is only the locking relay that gives problems.
1 - I tested first all the door lock actuators to make sure they are fine.
2 - I also checked wire continuity from the junction-box to the door lock actuators. Door lock wires are fine.
3 - I also 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). No power when it fails. You can still hear the relay click but no power sent to the actuators.
The relay energizes/activates itself when it gets an earth signal from the Body control ECU. I had a a second Body-ECU I could test. The second ECU showed the same relay behaviour (you hear the click but no power).
Good a simple and easy fix. I need to replace the door lock relay.
Well not so easy. This car is the RHD (right hand drive) version. The relay is located in the hidden side of the junction-box under the glove box. To reach this relay in the RHD version is an absolute nightmare. There is no space to detach the junction box as it is mostly hidden by the A/C pump. You would have to remove the whole dashboard. Worst design ever.
Plan B:
Get the wiring diagrams, 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.
My images:
Image A is a very simplified diagram of the central door lock in this car:
Image B is the EWD of the door lock/unlock relays at the junction box:
Image C is an image of the Junction box and the connections to the new relay that I have in mind:
Image D is a picture from the Junction Box wiring:
Thank you in advance,
Horsch
The central door lock relay fails in this car. You can hear it click but it doesn't lock doors. It only works fine when the weather gets cold.
Door unlocking (unlock relay) works fine. It is only the locking relay that gives problems.
1 - I tested first all the door lock actuators to make sure they are fine.
2 - I also checked wire continuity from the junction-box to the door lock actuators. Door lock wires are fine.
3 - I also 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). No power when it fails. You can still hear the relay click but no power sent to the actuators.
The relay energizes/activates itself when it gets an earth signal from the Body control ECU. I had a a second Body-ECU I could test. The second ECU showed the same relay behaviour (you hear the click but no power).
Good a simple and easy fix. I need to replace the door lock relay.
Well not so easy. This car is the RHD (right hand drive) version. The relay is located in the hidden side of the junction-box under the glove box. To reach this relay in the RHD version is an absolute nightmare. There is no space to detach the junction box as it is mostly hidden by the A/C pump. You would have to remove the whole dashboard. Worst design ever.
Plan B:
Get the wiring diagrams, 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.
My images:
Image A is a very simplified diagram of the central door lock in this car:
Image B is the EWD of the door lock/unlock relays at the junction box:
Image C is an image of the Junction box and the connections to the new relay that I have in mind:
Image D is a picture from the Junction Box wiring:
Thank you in advance,
Horsch
