Taillight not working

2016 TOYOTA COROLLA
12,000 MILES • 1.8L
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CTORRES
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When I turn on the light with the headlight dimmer switch taillights do not work just when I press brake pedal (stop light).
Please help me. I can use the car just in the day.
Mar 22, 2020 at 8:14 AM
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KASEKENNY
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This is most likely one of two issues. Clearly when pressing the brakes it shows the lights work so that means we most likely have a control issue. That means the switch itself is not signaling the BCM in the junction block that the lights are on (unless the head lights come on normally). Or the Body ECU is the issue. So we need to test two things. First if you have voltage going into the junction block on this circuit and second if the relay for the tail lamps is okay. It is not clear if this relay is used only for tail lamps or brake lamps as well so we need to check it and make sure.

Take a look at the diagrams and we can go from there.
Mar 22, 2020 at 8:24 AM
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KASEKENNY
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Actually I take that back. This relay appears to work for the headlights as well. So do the headlamps work normally?
Mar 22, 2020 at 8:25 AM
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CTORRES
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Morning KASKENNY.
I follow your instruction step by step. I can’t find the relay on the last picture . Please help me.
Mar 22, 2020 at 9:12 AM
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CTORRES
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Hello KASKENNY. I have a problem. when I was checking the system I don't know what I did and I lost radio, air-condition, headlight, power steering. please help me.
take care.
CTORRES
Mar 22, 2020 at 4:50 PM
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KASEKENNY
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Okay. I can't explain what happened but the body control module controls each one of these items.

When you were testing the switch in that video, were you on the input from the switch to the BCM or was that the output control from the BCM meaning the BCM was sending the lighting command for the tail lights?
Mar 22, 2020 at 5:46 PM
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CTORRES
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Good morning, KASEKENNY.
i was checking all fuses and I found one burnt. Thank goodness all is okay. (Radio A/C, power steering etc.)
Well, talking about taillights I want to tell you what I did.
In that video I founded wire to turn tail light and I checked it. The input from positive white wire on junction block. And the other side my test lamp I attached on the headlight switch and near to ECU. (Pic 1, 2) the wire is okay.
Mar 23, 2020 at 7:43 AM
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KASEKENNY
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Okay. So if the switch is working then I suspect the main body ECU is the issue which is part of the junction block. I would just turn the switch on and then check voltage coming out of the junction block that I highlighted. If you have voltage there then go to the lamp and check for voltage. If no voltage there then you have a wiring issue.
Mar 23, 2020 at 9:10 AM
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CTORRES
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Hi KASEKENNY, I checked tail fuse with my test lamp, and voltage coming out the junction block but no voltage there are. My issue is ECU Think I.
I was checking eBay some of them but I have a question for you.
1) If i buy a ECU I need to reprogramming?
2) buy a ECU with junction block?

Thanks for your patience, experience, time etc. All your tips and wiring diagram were amazing.

Take care.
CTORRES
Mar 24, 2020 at 1:14 PM
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KASEKENNY
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I agree that it appears this is what is needed. However, I don't think you need the junction block as well. I would just go off of price. If it is not much more then I would just get it. I attached the process to replace just the ECU. It doesn't mention needing to be programmed so I am assuming it does not. I have not actually replaced one of these personally so I am relying on the manual that would tell you to program it if needed.
Mar 24, 2020 at 3:30 PM
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CTORRES
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Hello KASEKENNY. Well I will buy the ECU and I will text to you. I wish the ECU do not need program.
Thanks again and think 2carpros and the expert people like you has been the best experience to fix my car.

Take care and I”ll text to you coming soon.

CTORRES
Mar 25, 2020 at 1:01 PM
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KASEKENNY
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Sounds great. Please keep us posted whenever you get it resolved. Thanks for the kind words. Look forward to hearing back from you with good news. Thanks
Mar 25, 2020 at 4:15 PM
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CTORRES
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Kasekenny. Hello,it is me again. finally the Junction Block and ECU are in Panama. I removed and performed operational test but does not have taillights. I’ll check all and text to you.
Thanks again.
CTORRES
Apr 3, 2020 at 11:20 AM
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KASEKENNY
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Sounds good. Keep us updated with what you find. Thanks.
Apr 4, 2020 at 8:51 AM
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CTORRES
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Hello. Well I have good news all lights are working. Thanks KASEKENNY and 2CarPros I appreciate your time, experience, all tips and all information about my car.
I not speak very well English but I improved and practiced my little English.
Thanks for all.

PS. Shift lock is no release so I’ll create a new topic for it, i wish you can help me.

Take care.

CRTORRES
Apr 4, 2020 at 11:49 AM
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KASEKENNY
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Sounds great. I responded on the other case as well. Unfortunately I didn't provide great news for you but I am sure we will work through it.

Thanks for coming back. We really appreciate it. By the way, I didn't notice that you didn't speak English so you are doing better than you think!
Apr 4, 2020 at 4:11 PM